WO2013038379A1 - Molten material for electrodes - Google Patents

Molten material for electrodes Download PDF

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Publication number
WO2013038379A1
WO2013038379A1 PCT/IB2012/054817 IB2012054817W WO2013038379A1 WO 2013038379 A1 WO2013038379 A1 WO 2013038379A1 IB 2012054817 W IB2012054817 W IB 2012054817W WO 2013038379 A1 WO2013038379 A1 WO 2013038379A1
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WIPO (PCT)
Prior art keywords
cations
molar
dopant
scandium
product
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PCT/IB2012/054817
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French (fr)
Inventor
Samuel Marlin
Caroline Véronique Laurence LEVY
Victor Orera Clemente
José PENA TORRE
Alodia ORERA UTRILLA
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Saint-Gobain Centre De Recherches Et D'etudes Europeen
Consejo Superior De Investigaciones Cientificas
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Publication of WO2013038379A1 publication Critical patent/WO2013038379A1/en

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Definitions

  • the present invention relates to a molten eutectic product, in particular for producing an element of a solid oxide fuel cell (SOFC), and in particular a cathode of such a cell.
  • SOFC solid oxide fuel cell
  • the invention also relates to processes for manufacturing said molten eutectic product.
  • FIG 1 schematically shows in section an example of a solid oxide fuel cell (SOFC) manufactured by a hot pressing process.
  • the battery 10 has first and second elementary cells, 12 and 14 respectively, separated by an interconnector layer 16.
  • the first and second elementary cells being of similar structure, only the first elementary cell 12 is described.
  • the first elementary cell 12 successively comprises an anode 18, an electrolyte layer 20 and a cathode 22.
  • the anode 18 consists of an active anode layer 24 (in English "anode functional layer", or AFL), in contact with the electrolyte layer 20, and a support anode layer 26.
  • the anode 18 is generally manufactured by a method of depositing on the support anode layer 26, an anode active layer 24, for example by screen printing (in English "screen printing").
  • the cathode 22 consists of a cathode functional layer 28 (cathode functional layer, or CFL), in contact with the electrolyte layer 20, and a support cathode layer 30.
  • CFL cathode functional layer
  • Fuel cells or materials that can be used for the production of fuel cells are for example described in WO2004 / 093235, EP 1 796 191, US 2007/0082254, EP 1 598 892 or EP 0 568 281.
  • the electrolyte used is generally a doped cerium oxide, for example with gadolinium, or stabilized zirconia, for example with yttrium. or scandium.
  • the cathode is generally made from "LSCF” materials, that is, materials of the formula La (i x ) Sr x Co (i- y ) Fe y O 3 - 6 , which are mixed conductors. i.e. both ionic and electronic conductors.
  • the "LSCF” can react with the zirconia doped with the electrolyte or with the cathode active layer to form new phases at their interface, in particular a SrZrO 3 phase, as described in "Time-dependent performance of mixed -conducting SOFC cathodes ", Solid State Ionics, Volume 177, Issues 19-25, p 1965-1968, especially in Figure 6, for the product Lao, 58Sr 0 , 4Coo, 2Feo, 80 3 _6. The presence of these phases can reduce the performance of the battery.
  • the cathode material has a coefficient of thermal expansion close to that of the electrolyte material, so as not to generate stresses that can lead to the creation of cracks and the decommissioning of the fuel cell.
  • An object of the invention is to respond, at least partially, to this need.
  • this object is achieved by means of a melted product consisting, for more than 50% of its mass, of a material having a eutectic structure and a composition such that:
  • a product according to the invention advantageously has properties that make it suitable for application to batteries of the SOFC type, in particular in a cathode and / or an active cathode layer.
  • said eutectic material represents more than 60%, more than 70%, more than 90%, more than 95%, more than 98%, or even substantially 100% of the mass of a melted product according to invention.
  • the 100% complement is preferably constituted by impurities and / or optionally doped zirconia and / or MnO manganese oxide and / or Mn 2 O 3 manganese oxide and / or Mn manganese oxide. 3 0 4 .
  • the molten product may have different chemical compositions and / or different structures (for example with a fibrous structure or a regular structure) than that of said eutectic material.
  • Said eutectic material may also include one or more of the following optional features (to the extent that they are not incompatible):
  • the constituents other than Zr0 2 , the dopant and Mn 3 0 4 represent less than 5%, less than 3%, less than 2%, less than 1% by weight;
  • the zirconia is not doped or is doped with an element chosen from cerium, yttrium, magnesium, calcium, scandium, aluminum and their mixtures, preferably chosen from cerium, a mixture of scandium; and aluminum, a mixture of scandium and cerium, and yttrium. More preferably, the dopant is yttrium; More than 90%, more than 95%, or even substantially 100%, in molar percentage, of the zirconia Zr0 2 is doped;
  • the molar dopant content of the ZrO 2 zirconia is greater than 5% and / or less than 25%;
  • zirconia Zr0 2 is doped only with yttrium;
  • the molar content of yttrium is preferably greater than 5%, preferably greater than 10%, preferably greater than 15%, and or less than 22%, preferably less than 21%, preferably substantially equal to 16% or substantially equal to 20%;
  • Zirconia Zr0 2 is doped only with scandium;
  • the molar content of scandium based on the sum of the molar contents of zirconium cations and scandium cations, is preferably greater than 14% and / or less than 22%, preferably substantially equal to 20%;
  • Zr0 2 zirconia is doped only with a mixture of scandium on the one hand and aluminum and / or cerium on the other hand;
  • the molar content of scandium is preferably greater than 14% and / or less than 22%, preferably substantially equal to 20%; and or
  • the molar content of aluminum on the basis of the sum of the molar concentrations of zirconium, scandium, aluminum and cerium cations is preferably greater than 1% and / or less than 3%, preferably substantially equal to 2%; and or
  • the molar content of cerium on the basis of the sum of the molar contents of zirconium, scandium, aluminum and cerium cations is preferably greater than 0.5% and / or less than 1.5%, preferably substantially equal to 1%; %
  • the zirconia, the manganese oxide ⁇ 3 0 4 and the dopant together represent preferably more than 90%, more than 95%, more than 98%, more than 99%, or even substantially 100%) of said molten material, or even of eutectic product according to the invention, in percentage by mass;
  • the 100% complement) consists of impurities;
  • the eutectic material has an impurity content of less than 5%, less than 3%, preferably less than 2%, more preferably less than 1% by mass percentage;
  • the eutectic material preferably has a fibrous structure
  • At least a part of the manganese of the eutectic material preferably more than 5 atom%, more than 10 atom%, or even more than 15 atom%, is solubilized in the zirconia.
  • the solubility of manganese in zirconia can be in particular equal to 16 atom%.
  • a melted product according to the invention may be in the form of a molten ball, a molten plate, a molten block, or a particle or a powder resulting from a grinding of such a melted plate or such a melted block.
  • the present invention also relates to a powder of melted product particles according to the invention.
  • the median size D 50 is greater than 0.3 ⁇ , or even greater than 0.5 ⁇ , or even greater than 1 ⁇ , or even greater than 2 ⁇ , and / or less than 80 ⁇ , or even less than 50 ⁇ , or even less at 40 ⁇ ;
  • the powder has a median size greater than 0.3 ⁇ , or even greater than 0.5 ⁇ , or even greater than 1 ⁇ , and less than
  • the powder has a median size greater than 10 ⁇ , or even greater than 20 microns, or even greater than 30 ⁇ , or even greater than 40 ⁇ , and / or less than 80 microns, or even less than 50. microns; Preferably, the median size is about 45 microns; The characteristics of a cathode layer supporting the SOFC stack obtained from such a powder are advantageously improved;
  • the maximum size of the powder is less than 200 ⁇ , or even less than 150 ⁇ , or even less than 110 ⁇ ;
  • the distribution of the form factor R of the powder is such that: less than 90% or even less than 80% of the particles of the powder have a form factor R greater than 1.5, and / or
  • the particles of the powder are ground particles, that is to say resulting from a grinding operation of a molten product, for example in the form of larger particles or blocks. Such grinding gives a particular shape to the ground particles.
  • the invention also relates to a preform or "green part" obtained by shaping a powder according to the invention, a sintered product obtained from such a preform, in particular a sintered part or a sintered layer.
  • the preform or the sintered product may in particular be in the form of a layer of thickness less than 2 mm, less than 1 mm or less than 500 ⁇ .
  • the sintered product may in particular have a total porosity greater than 20%, preferably between 25% and 50% by volume, preferably between 25% and 45% by volume.
  • the present invention also relates to an electrode, in particular to a cathode, comprising a region, in particular a functional cathode, said electrode, in particular said functional cathode being constituted from a powder according to the invention.
  • the invention also relates to an elementary cell of a battery solid oxide fuel comprising an electrode, preferably a cathode according to the invention, and such a fuel cell.
  • the invention finally relates to a manufacturing method, called "general manufacturing process", comprising the following successive steps:
  • step c) the raw materials being chosen so that at the end of step c), the molten product obtained is in accordance with the invention, the cooling in step c) involving a contacting of the molten material and or the molten product with a fluid comprising oxygen.
  • the oven used in step b) is chosen from an induction furnace, a plasma torch, an arc furnace or a laser.
  • a product is conventionally called "molten” when it is obtained by a process involving a melting of raw materials in the form of a liquid mass (or “molten material”), then a solidification of this liquid mass by cooling. .
  • a liquid mass may comprise solid particles, but in insufficient quantity to stiffen said mass.
  • eutectic is a structure or morphology obtained by melting a eutectic composition and then hardening the melt by cooling.
  • Solidification microstructure Eutectic and peritectic
  • a eutectic structure can be of two types: regular (normal) or irregular
  • a regular structure can be in particular fibrous (Figure 5A) or lamellar (Figure 5B).
  • the regular structure of the eutectic material of a product according to the invention preferably has a fibrous morphology, in which there is a marked crystallographic relationship between the phases of the eutectic.
  • the fibrous morphology corresponds to a morphology in which one of the phases, in the form of fibers, is embedded in a continuous matrix formed by the second phase. The axis of the fibers is then parallel to the direction of propagation of the growth front D f (FIG. 5A).
  • a fibrous structure may in particular result from a process for the manufacture by melting of an eutectic mixture comprising a solidification step at a speed greater than 0.17 K / s, preferably greater than 1.7 K / s, greater than 8 , 5 K s, greater than 17 K / s, greater than 34 K / s, greater than 50 K / s, or even greater than 85 K / s.
  • a "dopant" of zirconia is a metal cation other than the zirconium cation, integrated within the Zr0 2 crystal lattice, most often in solid solution.
  • the dopant may be present as an insertion and / or substitution cation within the zirconia.
  • zirconia Zr0 2 is said to be "doped at x% with a dopant"
  • this conventionally means that, in said doped zirconia, the amount of dopant is the molar percentage of dopant cations on the basis of the total quantity of cations. of dopant and zirconium cations. For example, in a zirconia doped with 20 mol% yttrium (Y), 20% of the zirconium cations are replaced by yttrium cations.
  • zirconia doped with 20% of scandium (Se) and 1% of cerium 21% of the zirconium cations are replaced by 20% of scandium cations and 1% of cerium cations.
  • Zr0 2 ", “zirconia” and “zirconium oxide” are synonymous.
  • Zr0 2 + dopant is meant the sum of the molar contents of zirconium cations and dopant.
  • a precursor of Zr0 2 , Mn 3 0 4 or dopant is a compound capable of leading to the formation of these oxides or dopant, respectively, by a process comprising a melting and then a solidification by cooling.
  • Zirconia doped with a dopant or with an oxide of said dopant is a particular example of a precursor of said dopant.
  • particle size is meant the size of a particle conventionally given by a particle size distribution characterization performed with a laser granulometer.
  • the laser granulometer used here is a Partica LA-950 from the company HORIBA.
  • the percentiles or "percentiles" (D 10 ), 50 (D 50 ), 90 (D 90 ) and 99.5 (D 9 9 15 ) of a powder are the particle sizes corresponding to the percentages, by mass, of 10%, 50%, 90% and 99.5%, respectively, on the cumulative particle size distribution curve of the powder particles, the particle sizes being ranked in ascending order. For example, 10% by weight of the particles of the powder have a size less than D 10 and 90% of the particles by mass have a size greater than D 10 . Percentiles can be determined using a particle size distribution using a laser granulometer.
  • the “maximum size” is the 99.5 percentile (p99, 5 ) of said powder.
  • the so-called “median size” is the percentile D50, that is to say the size dividing the particles into first and second populations equal in mass, these first and second populations comprising only particles having a larger size, or smaller respectively, at the median size.
  • the "ratio of shape” R is the ratio between the largest apparent dimension, or “length” L, and the smallest apparent dimension, or “width” W, of a particle.
  • the length and the width of a particle are classically evaluated by the following method. After taking a representative sample of the particles of the powder, these particles are partially embedded in the resin and undergo polishing capable of making possible a polished surface observation.
  • the shape factor measurements are made from images of these polished surfaces, these images being acquired with an electron scanning microscope (SEM), in secondary electrons, with an acceleration voltage of 10 kV and a magnification of x100. (This represents 1 ⁇ per pixel on the SEM used). These images are of preference acquired in areas where the particles are best separated, in order to subsequently facilitate the determination of the form factor.
  • SEM electron scanning microscope
  • the largest apparent dimension called length L
  • W the smallest apparent dimension
  • these dimensions are measured using an image processing software, such as for example VISILOG marketed by the company NOESIS.
  • the form factor R L / W is calculated.
  • impurities is meant the inevitable constituents introduced involuntarily and necessarily with the raw materials or resulting from reactions with these constituents. Impurities are not necessary constituents, but only tolerated.
  • the compounds forming part of the group of oxides, nitrides, oxynitrides, carbides, oxycarbides, carbonitrides and metallic species of sodium and other alkalis, iron, vanadium and chromium are impurities if their presence is not desired.
  • FIG. 1 is a diagrammatic sectional view of a solid oxide fuel cell (SOFC);
  • SOFC solid oxide fuel cell
  • FIGS. 2, 3 and 4 represent photographs of the molten eutectic products of ZrC " 2 doped with 8 mol% Y 2 O 3 - Mn 3 0 4 of Examples 2, 3 and 4, respectively, according to the invention, taken using a scanning electron microscope (SEM);
  • FIG. 5 shows diagrams illustrating regular eutectic (FIGS. 5A and 5B) and irregular (FIGS. 5C and 5D) morphologies.
  • the zirconia doped with 16 mol% of Y appears in white color and the manganese oxide Mn 3 0 4 appears gray in color.
  • a melted product according to the invention may in particular be manufactured according to steps a) to e).
  • the feedstock is conventionally adapted so that the manufacturing process leads, at the end of step c), to a molten product according to the invention optionally having one or more optional features described above.
  • the dopant can be added separately from the zirconia in the feedstock. It is also possible to add, in the starting charge, the doped zirconia.
  • the oxides Zr0 2 , ⁇ 3 0 4 , Mn 2 0 3 , MnO, the dopants of the zirconia and their precursors preferably constitute, with the impurities, 100% of the oxides of the feedstock.
  • the impurities are such that, in molar percentages based on the oxides of the feedstock:
  • step b) it is possible in particular to use an induction furnace, a plasma torch, an arc furnace or a laser.
  • an arc or induction furnace is used.
  • step b) the melting is preferably carried out under oxidizing conditions.
  • the oxidizing conditions in step b) can be maintained in step c).
  • Step c) preferably comprises bringing the molten material into contact with a fluid comprising oxygen.
  • the fluid comprises more than 10% oxygen, more than 20% oxygen, by volume.
  • the fluid is air.
  • the molten product obtained at the end of step c) can also be brought into contact with such a fluid comprising oxygen.
  • the cooling rate is preferably greater than 0.17 K / s, preferably greater than 1.7 K / s, or even greater than 8.5 K s, or even greater than 17 K / s , even greater than 34 K / s, or even greater than 50 K / s, or even greater than 85 K / s.
  • Such cooling rate coupled with a contacting of the melt and / or the melt with a fluid comprising oxygen advantageously makes it possible to maintain substantially constant the manganese oxide content in the form Mn 3 0 4 (no or little conversion to Mn 2 0 3 ).
  • step d) the melt product from step c) can be milled to facilitate the effectiveness of subsequent steps.
  • the granulometry of the crushed product is adapted according to its destination. If necessary, the ground particles undergo a granulometric selection operation, for example by sieving.
  • the crushed particles, and optionally sieved may in particular have a size greater than 0.1 ⁇ , or even greater than 1 ⁇ , or even greater than 0.3 ⁇ , or even greater than 0.5 ⁇ , or even greater than 1 ⁇ , or even greater at 15 ⁇ , or even greater than 20 ⁇ , and / or less than 6 mm, or even less than 4 mm, or even less than 3 mm, or even less than 70 ⁇ , or even less than 50 ⁇ .
  • step e) the product is shaped, in particular to be sintered. All conventional shaping and sintering techniques can be used.
  • the sintering is carried out in situ, that is to say after the melted product, possibly ground, has been placed in its service position, for example in the form of a cathode layer. .
  • a product according to the invention may have a high total porosity, typically greater than 20% and / or less than 60%.
  • the porosity of said product is of great importance because the pores are the seat of part of the catalysis reactions necessary for the operation of the fuel cell. Pores are also the means of conveying a gas, usually air, within the cathode.
  • the invention also relates to a first particular manufacturing method comprising the steps a), b) described above, and a step c) comprising the following steps:
  • Ci solidification of these liquid droplets by contact with a fluid comprising oxygen, so as to obtain melt particles according to the invention.
  • a first particular manufacturing method may further include one or more of the optional features of the general manufacturing method listed above.
  • step c beads according to the invention are obtained in a melted product according to the invention.
  • the dispersion steps Ci ') and the solidification Ci ") are substantially simultaneous, the means used for the dispersion causing the melt to cool, for example, the dispersion results from a blowing of gas comprising oxygen, for example air, through the melting material, the temperature of said gas being adapted to the desired solidification rate.
  • the contact between the droplets and the fluid comprising oxygen may be of variable duration. Preferably, however, a contact is maintained between the droplets and this fluid until complete solidification of said droplets.
  • step c1) the solidification rate of the liquid droplets is preferably greater than 8.5 K / s, or even greater than 17 K / s, or even greater than 25.5 K / s.
  • This second particular manufacturing method may also include one or more of the optional features of the general manufacturing method listed above.
  • a mold is used which allows rapid cooling.
  • a mold capable of forming a block in the form of a plate, and preferably a mold as described in US 3,993,119.
  • step c 2 ') and / or in step c 2 ") and / or in step c 2 "') and / or after step c 2 "') contact is made with a oxidizing fluid said melt and / or cast material being solidified in the mold and / or the demolded block.
  • the fluid comprising oxygen used in step c 2 ') and / or in step c 2 ") and / or in step c 2 "') and / or after step c 2 " ), preferably gaseous, preferably air, may be identical.
  • the solidification rate of the liquid droplets is preferably greater than 8.5 K / s, or even greater than 17 K / s, or even greater than 25.5 K / s.
  • step c 2 "') demolding is preferably carried out before complete solidification of the block, preferably the block is demolded as soon as it has sufficient rigidity to substantially maintain its shape. fluid comprising oxygen is then increased.
  • the first and second particular methods are industrial processes for manufacturing large quantities of products, with good yields.
  • a powder of a melted product according to the invention may in particular be used to manufacture a porous product according to the invention, in particular a porous cathode layer and / or a porous cathode active layer, for example by following a process comprising the successive stages:
  • step A) sintering of said powder thus shaped.
  • the product powder according to the invention used in step A) may in particular be manufactured according to steps a) to f) described above.
  • step B the powder may be deposited in the form of a layer.
  • step C the shaped powder is sintered according to conventional sintering techniques, preferably by hot pressing.
  • the products of the examples according to the invention 2, 3 and 4 were obtained by melting in a floating zone under laser heating ("Laser floating zone" in English), using a C0 2 laser with a power of 600 Watts.
  • the raw materials used are as follows:
  • a zirconia powder doped with 16 mol% of yttrium marketed by the company TOSOH under the name 8YSZ, of median size equal to 0.25 ⁇ and of purity equal to 99.9%;
  • MnO Manganese oxide powder sold by Sigma Aldrich under the name MnO Manganese (II) oxide powder - 60 Mesh, of purity equal to 99%.
  • the raw materials in powder are chosen and their quantities adapted according to the product to be manufactured.
  • the raw material mixture consists of 73% MnO and 27% 8YSZ, in percentages by weight. These raw materials are intimately mixed in a ball mill. When mixing in the ball mill, a solution of 5% PVA and 95% water is added in proportions of 1 ml per 1.5 to 2 g of powder mixture. The mixture thus obtained is put in the form of chopsticks by cold isostatic pressing ("Cold Isostatic pressing" or "CIP” in English) at 200 Mbar for 3 to 4 minutes.
  • the rods obtained are then sintered under air as follows:
  • the rods thus sintered are then moved in translation (without rotation of the rods) through the beam of a laser set at 60W. They thus undergo a fusion in a floating zone under laser heating, under air, with a constant speed of growth. between 50 and 500 mm / h, which corresponds to a cooling rate of between 8.5 and about 85 K / s. After directional solidification, the product of the rods is a melted product according to the invention.
  • the Lao product, 58Sro, 4 Coo, 2 Feo, 8 0 3 _ 6 of Comparative Example 1 is the product described in "Time-dependent performance of mixed-conduct SOFC cathodes," Solid State Ionics, Volume 177, Issues 19 -25, p 1965-1968.
  • the content of impurities was less than 2%.
  • the nature of the manganese oxide is demonstrated by X-ray diffraction.
  • the X-ray diffracted manganese oxide is ⁇ 3 0 4 .
  • Vr cooling rate during manufacture of the molten product
  • the products according to Examples 2, 3 and 4 have a coefficient of thermal expansion at a temperature below 1000 ° C. of the order of 10 ⁇ 10 6 K -1 , which is of the same order of magnitude as that of the doped zirconia. Furthermore, the products according to the invention do not form an undesirable phase of SrZr0 3 when they are used in SOFC cell electrodes, as is the case for the product according to Comparative Example 1. More generally, they present a low reactivity vis-à-vis the doped zirconia which can constitute the electrolyte of a SOFC stack. As it is now clear, the invention provides a new molten product comprising a eutectic material Zr0 2 possibly doped Mn 3 0 4 perfectly suitable for the manufacture of SOFC batteries.

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Abstract

The invention relates to a molten material comprising, for more than 50% of the mass thereof, a material having a eutectic structure and a composition such that: 42.5% - 46.5% (ZrO2 + optional zirconia dopant), and 53.5% - 57.5% Mn3O4.

Description

Produit fondu pour électrode  Molten electrode product
Domaine technique Technical area
La présente invention se rapporte à un produit d'eutectique fondu, en particulier pour fabriquer un élément d'une pile à combustible à oxyde solide (SOFC), et notamment une cathode d'une telle pile. L'invention se rapporte également à des procédés de fabrication dudit produit d'eutectique fondu.  The present invention relates to a molten eutectic product, in particular for producing an element of a solid oxide fuel cell (SOFC), and in particular a cathode of such a cell. The invention also relates to processes for manufacturing said molten eutectic product.
Etat de la technique State of the art
La figure 1 représente schématiquement en coupe un exemple de pile 10 à combustible à oxyde solide (SOFC), fabriquée par un procédé de pressage à chaud. La pile 10 comporte des première et deuxième cellules élémentaires, 12 et 14 respectivement, séparées par une couche d' interconnecteur 16. Les première et deuxième cellules élémentaires étant de structure similaire, seule la première cellule élémentaire 12 est décrite. La première cellule élémentaire 12 comporte successivement une anode 18, une couche d'électrolyte 20 et une cathode 22. L'anode 18 est constituée d'une couche active d'anode 24 (en anglais « anode functional layer », ou AFL), en contact avec la couche d'électrolyte 20, et une couche anode support 26. L'anode 18 est généralement fabriquée par un procédé consistant à déposer sur la couche d'anode support 26, une couche active d'anode 24, par exemple par sérigraphie (en anglais « screen printing »). A ce stade, les couches 24 et 26 peuvent être à base de précurseur du matériau d'anode final. Une consolidation par frittage est ensuite réalisée. La cathode 22 est constituée d'une couche active de cathode 28 (en anglais « cathode functional layer », ou CFL), en contact avec la couche d'électrolyte 20, et une couche cathode support 30.  Figure 1 schematically shows in section an example of a solid oxide fuel cell (SOFC) manufactured by a hot pressing process. The battery 10 has first and second elementary cells, 12 and 14 respectively, separated by an interconnector layer 16. The first and second elementary cells being of similar structure, only the first elementary cell 12 is described. The first elementary cell 12 successively comprises an anode 18, an electrolyte layer 20 and a cathode 22. The anode 18 consists of an active anode layer 24 (in English "anode functional layer", or AFL), in contact with the electrolyte layer 20, and a support anode layer 26. The anode 18 is generally manufactured by a method of depositing on the support anode layer 26, an anode active layer 24, for example by screen printing (in English "screen printing"). At this stage, the layers 24 and 26 may be precursor-based of the final anode material. Consolidation by sintering is then performed. The cathode 22 consists of a cathode functional layer 28 (cathode functional layer, or CFL), in contact with the electrolyte layer 20, and a support cathode layer 30.
Des piles à combustible ou des matériaux utilisables pour la fabrication de piles à combustible sont par exemple décrits dans WO2004/093235, EP 1 796 191, US 2007/0082254, EP 1 598 892 ou EP 0 568 281.  Fuel cells or materials that can be used for the production of fuel cells are for example described in WO2004 / 093235, EP 1 796 191, US 2007/0082254, EP 1 598 892 or EP 0 568 281.
Parmi les piles à combustible, on distingue les piles à combustible pouvant fonctionner « basses » températures, c'est-à-dire à des températures inférieures ou égales à 850°C. Dans de telles piles à combustible, l'électrolyte utilisé, se présentant en général sous la forme d'une couche mince, est généralement en un oxyde de cérium dopé, par exemple au gadolinium, ou en zircone stabilisée, par exemple à l'yttrium ou au scandium. La cathode est en général fabriquée à partir de matériaux « LSCF », c'est-à-dire des matériaux de formule La(i_x)SrxCo(i_y)Fey03_6, qui sont des conducteurs mixtes, c'est-à-dire à la fois des conducteurs ioniques et électroniques. Or les « LSCF » peuvent réagir avec la zircone dopée de l'électrolyte ou de la couche active de cathode pour former de nouvelles phases à leur interface, en particulier une phase SrZr03, comme cela est décrit dans « Time-dependent performance of mixed-conducting SOFC cathodes », Solid State Ionics, Volume 177, Issues 19-25, p 1965-1968, notamment en figure 6, pour le produit Lao,58Sr0,4Coo,2Feo,803_6. La présence de ces phases peut diminuer les performances de la pile. Among the fuel cells, there are fuel cells that can operate "low" temperatures, that is to say at temperatures below or equal to 850 ° C. In such fuel cells, the electrolyte used, generally in the form of a thin layer, is generally a doped cerium oxide, for example with gadolinium, or stabilized zirconia, for example with yttrium. or scandium. The cathode is generally made from "LSCF" materials, that is, materials of the formula La (i x ) Sr x Co (i- y ) Fe y O 3 - 6 , which are mixed conductors. i.e. both ionic and electronic conductors. However, the "LSCF" can react with the zirconia doped with the electrolyte or with the cathode active layer to form new phases at their interface, in particular a SrZrO 3 phase, as described in "Time-dependent performance of mixed -conducting SOFC cathodes ", Solid State Ionics, Volume 177, Issues 19-25, p 1965-1968, especially in Figure 6, for the product Lao, 58Sr 0 , 4Coo, 2Feo, 80 3 _6. The presence of these phases can reduce the performance of the battery.
De plus, il est préférable que le matériau de cathode présente un coefficient de dilatation thermique proche de celui du matériau de l'électrolyte, afin de ne pas générer de contraintes pouvant amener à la création de fissures et à la mise hors d'usage de la pile à combustible. In addition, it is preferable that the cathode material has a coefficient of thermal expansion close to that of the electrolyte material, so as not to generate stresses that can lead to the creation of cracks and the decommissioning of the fuel cell.
Afin d'augmenter les performances des piles SOFC fonctionnant à basses températures, il existe donc un besoin pour un produit conducteur mixte, apte à ne former qu'une faible quantité de nouvelles phases lorsqu'il est en contact avec une poudre de zircone dopée, en particulier la phase SrZr03 et présentant un coefficient de dilatation thermique proche de celui du matériau de l'électrolyte, en particulier lorsque celui-ci est une zircone dopée. Un but de l'invention est de répondre, au moins partiellement, à ce besoin. In order to increase the performance of SOFC batteries operating at low temperatures, there is therefore a need for a mixed conductive product, capable of forming only a small amount of new phases when in contact with a doped zirconia powder, in particular the SrZr0 3 phase and having a coefficient of thermal expansion close to that of the electrolyte material, in particular when the latter is a doped zirconia. An object of the invention is to respond, at least partially, to this need.
Résumé de l'invention Summary of the invention
Selon l'invention, on atteint ce but au moyen d'un produit fondu constitué, pour plus de 50% de sa masse, d'un matériau présentant une structure eutectique et une composition telle que :  According to the invention, this object is achieved by means of a melted product consisting, for more than 50% of its mass, of a material having a eutectic structure and a composition such that:
- (Zr02 + dopant de la zircone optionnel) : 42,5% - 46,5%, - (Zr0 2 + dopant of the optional zirconia): 42.5% - 46.5%,
- Mn304 : 53,5% - 57,5%, Mn 3 O 4 : 53.5% - 57.5%,
en pourcentages molaires sur la base de la somme des teneurs en Zr02, en dopant et en Mn304. in molar percentages based on the sum of the Zr0 2 , dopant and Mn 3 0 4 contents.
Ce matériau est appelé ci-après « matériau eutectique ».  This material is hereinafter referred to as "eutectic material".
Comme on le verra plus en détail dans la suite de la description, un produit selon l'invention présente avantageusement des propriétés qui le rendent adapté à l'application à des piles du type SOFC, en particulier dans une cathode et/ou une couche active de cathode. As will be seen in more detail in the following description, a product according to the invention advantageously has properties that make it suitable for application to batteries of the SOFC type, in particular in a cathode and / or an active cathode layer.
De préférence, ledit matériau eutectique représente plus de 60%, plus de 70%>, plus de 90%), plus de 95%, plus de 98%>, voire sensiblement 100% de la masse d'un produit fondu selon l'invention. Le complément à 100% est de préférence constitué d'impuretés et/ou de zircone, éventuellement dopé et/ou d'oxyde de manganèse MnO et/ou d'oxyde de manganèse Mn203 et/ou d'oxyde de manganèse Mn304. Preferably, said eutectic material represents more than 60%, more than 70%, more than 90%, more than 95%, more than 98%, or even substantially 100% of the mass of a melted product according to invention. The 100% complement is preferably constituted by impurities and / or optionally doped zirconia and / or MnO manganese oxide and / or Mn 2 O 3 manganese oxide and / or Mn manganese oxide. 3 0 4 .
Dans les régions qui ne sont pas en ledit matériau eutectique, le produit fondu peut présenter des compositions chimiques différentes et/ou des structures différentes (par exemple à structure fibreuse ou à structure régulière) de celle dudit matériau eutectique. In regions that are not in said eutectic material, the molten product may have different chemical compositions and / or different structures (for example with a fibrous structure or a regular structure) than that of said eutectic material.
Ledit matériau eutectique peut encore comporter une ou plusieurs des caractéristiques optionnelles suivantes (dans la mesure où elles ne sont pas incompatibles) : Said eutectic material may also include one or more of the following optional features (to the extent that they are not incompatible):
- Pour un total de 100%), en pourcentages molaires sur la base de la somme des teneurs en Zr02, en dopant et en Mn304, - For a total of 100%), in molar percentages based on the sum of the Zr0 2 , dopant and Mn 3 0 4 contents,
- (Zr02 + dopant) : 43% - 46% - (Zr0 2 + dopant): 43% - 46%
- Mn304 : 54% - 57%, - Mn 3 0 4 : 54% - 57%,
- De préférence  - Preferably
- (Zr02 + dopant) : 43,5% - 45,5% - (Zr0 2 + dopant): 43.5% - 45.5%
- Mn304 : 54,5% - 56,5%, - Mn 3 0 4 : 54.5% - 56.5%,
- De préférence - Preferably
- (Zr02 + dopant) : 44% - 45% - (Zr0 2 + dopant): 44% - 45%
- Mn304 : 55% - 56%, - Mn 3 0 4 : 55% - 56%,
- De préférence  - Preferably
- (Zr02 + dopant) : 44,5% - (Zr0 2 + dopant): 44.5%
- Mn304 : 55,5%, Mn 3 O 4 : 55.5%,
- Dans le matériau eutectique, les constituants autres que Zr02, le dopant et Mn304 représentent moins de 5%, moins de 3%, moins de 2%, moins de 1% en masse ; In the eutectic material, the constituents other than Zr0 2 , the dopant and Mn 3 0 4 represent less than 5%, less than 3%, less than 2%, less than 1% by weight;
- La zircone n'est pas dopée ou est dopée avec un élément choisi parmi le cérium, l'yttrium, le magnésium, le calcium, le scandium, l'aluminium et leurs mélanges, de préférence choisi parmi le cérium, un mélange de scandium et d'aluminium, un mélange de scandium et de cérium, et l'yttrium. De préférence encore, le dopant est l'yttrium ; Plus de 90%, plus de 95%, voire sensiblement 100%, en pourcentage molaire, de la zircone Zr02 est dopé ; The zirconia is not doped or is doped with an element chosen from cerium, yttrium, magnesium, calcium, scandium, aluminum and their mixtures, preferably chosen from cerium, a mixture of scandium; and aluminum, a mixture of scandium and cerium, and yttrium. More preferably, the dopant is yttrium; More than 90%, more than 95%, or even substantially 100%, in molar percentage, of the zirconia Zr0 2 is doped;
La teneur molaire en dopant de la zircone Zr02, sur la base de la somme des teneurs en cations zirconium et en cations de dopant, est supérieure à 5% et/ou inférieure à 25% ; De préférence, la zircone Zr02 est dopée seulement avec l'yttrium ; La teneur molaire en yttrium, sur la base de la somme des teneurs molaires en cations de zirconium et en cations d'yttrium, est de préférence supérieure à 5%, de préférence supérieure à 10%, de préférence supérieure à 15%, et/ou inférieure à 22%, de préférence inférieure à 21%, de préférence sensiblement égale à 16% ou sensiblement égale à 20% ; The molar dopant content of the ZrO 2 zirconia, based on the sum of the zirconium cation and dopant cation contents, is greater than 5% and / or less than 25%; Preferably, zirconia Zr0 2 is doped only with yttrium; The molar content of yttrium, based on the sum of the molar contents of zirconium cations and yttrium cations, is preferably greater than 5%, preferably greater than 10%, preferably greater than 15%, and or less than 22%, preferably less than 21%, preferably substantially equal to 16% or substantially equal to 20%;
La zircone Zr02 est dopée seulement avec du scandium ; La teneur molaire en scandium, sur la base de la somme des teneurs molaires en cations de zirconium et en cations de scandium, est de préférence supérieure à 14% et/ou inférieure à 22%, de préférence sensiblement égale à 20% ; Zirconia Zr0 2 is doped only with scandium; The molar content of scandium, based on the sum of the molar contents of zirconium cations and scandium cations, is preferably greater than 14% and / or less than 22%, preferably substantially equal to 20%;
La zircone Zr02 est dopée seulement avec un mélange de scandium d'une part et d'aluminium et/ou de cérium d'autre part ; Dans ce mode de réalisation : Zr0 2 zirconia is doped only with a mixture of scandium on the one hand and aluminum and / or cerium on the other hand; In this embodiment:
- la teneur molaire en scandium, sur la base de la somme des teneurs molaires en cations de zirconium, scandium, aluminium et cérium est de préférence supérieure à 14% et/ou inférieure à 22%, de préférence sensiblement égale à 20% ; et/ou  the molar content of scandium, on the basis of the sum of the molar contents of zirconium, scandium, aluminum and cerium cations, is preferably greater than 14% and / or less than 22%, preferably substantially equal to 20%; and or
- la teneur molaire en aluminium sur la base de la somme des teneurs molaires en cations de zirconium, scandium, aluminium et cérium est de préférence supérieure à 1% et/ou inférieure à 3%, de préférence sensiblement égale à 2% ; et/ou  the molar content of aluminum on the basis of the sum of the molar concentrations of zirconium, scandium, aluminum and cerium cations is preferably greater than 1% and / or less than 3%, preferably substantially equal to 2%; and or
- la teneur molaire en cérium sur la base de la somme des teneurs molaires en cations de zirconium, scandium, aluminium et cérium est de préférence supérieure à 0,5% et/ou inférieure à 1 ,5%, de préférence sensiblement égale à 1% ;  the molar content of cerium on the basis of the sum of the molar contents of zirconium, scandium, aluminum and cerium cations is preferably greater than 0.5% and / or less than 1.5%, preferably substantially equal to 1%; %
La zircone, l'oxyde de manganèse Μη304 et le dopant représentent ensemble de préférence plus de 90%, plus de 95%, plus de 98%, plus de 99%, voire sensiblement 100%) dudit matériau fondu, voire du produit eutectique selon l'invention, en pourcentage massique ; De préférence, le complément à 100%) est constitué par des impuretés ; - Le matériau eutectique présente une teneur en impuretés inférieure à 5%, inférieure à 3%, de préférence inférieure à 2%, de préférence encore inférieure à 1% en pourcentage massique ; The zirconia, the manganese oxide Μη 3 0 4 and the dopant together represent preferably more than 90%, more than 95%, more than 98%, more than 99%, or even substantially 100%) of said molten material, or even of eutectic product according to the invention, in percentage by mass; Preferably, the 100% complement) consists of impurities; The eutectic material has an impurity content of less than 5%, less than 3%, preferably less than 2%, more preferably less than 1% by mass percentage;
- Le matériau eutectique présente de préférence une structure fibreuse ;  - The eutectic material preferably has a fibrous structure;
- Au moins une partie du manganèse du matériau eutectique, de préférence plus de 5 atome%, plus de 10 atome%, voire plus de 15 atome%, est solubilisée dans la zircone. La solubilité du manganèse dans la zircone peut être en particulier égale à 16 atome%. At least a part of the manganese of the eutectic material, preferably more than 5 atom%, more than 10 atom%, or even more than 15 atom%, is solubilized in the zirconia. The solubility of manganese in zirconia can be in particular equal to 16 atom%.
Un produit fondu selon l'invention peut se présenter sous la forme d'une bille fondue, d'une plaque fondue, d'un bloc fondu, ou d'une particule ou d'une poudre résultant d'un broyage d'une telle plaque fondue ou d'un tel bloc fondu. A melted product according to the invention may be in the form of a molten ball, a molten plate, a molten block, or a particle or a powder resulting from a grinding of such a melted plate or such a melted block.
La présente invention se rapporte encore à une poudre de particules de produit fondu selon l'invention. The present invention also relates to a powder of melted product particles according to the invention.
Une poudre selon l'invention peut encore comporter une ou plusieurs des caractéristiques optionnelles suivantes :  A powder according to the invention may also comprise one or more of the following optional characteristics:
- La taille médiane D50 est supérieure à 0,3 μιη, voire supérieure à 0,5 μιη, voire supérieure à 1 μιη, voire supérieure à 2 μιη, et/ou inférieure à 80 μιη, voire inférieure à 50 μιη, voire inférieure à 40 μιη ; - The median size D 50 is greater than 0.3 μιη, or even greater than 0.5 μιη, or even greater than 1 μιη, or even greater than 2 μιη, and / or less than 80 μιη, or even less than 50 μιη, or even less at 40 μιη;
- Dans un premier mode de réalisation particulier, la poudre présente une taille médiane supérieure à 0,3 μιη, voire supérieure à 0,5 μιη, voire supérieure à 1 μιη, et inférieure à - In a first particular embodiment, the powder has a median size greater than 0.3 μιη, or even greater than 0.5 μιη, or even greater than 1 μιη, and less than
10 μιη, voire inférieure à 4 μιη. Les caractéristiques d'une couche active de cathode de la pile SOFC obtenue à partir d'une telle poudre en sont avantageusement améliorées ;10 μιη, or even less than 4 μιη. The characteristics of an active cathode layer of the SOFC stack obtained from such a powder are advantageously improved;
- Dans un deuxième mode de réalisation particulier, la poudre présente une taille médiane supérieure à 10 μιη, voire supérieure à 20 microns, voire supérieure à 30 μιη, voire supérieure à 40 μιη, et/ou inférieure à 80 microns, voire inférieure à 50 microns ; De préférence, la taille médiane est égale à environ 45 microns ; Les caractéristiques d'une couche de cathode support de la pile SOFC obtenue à partir d'une telle poudre en sont avantageusement améliorées ; In a second particular embodiment, the powder has a median size greater than 10 μιη, or even greater than 20 microns, or even greater than 30 μιη, or even greater than 40 μιη, and / or less than 80 microns, or even less than 50. microns; Preferably, the median size is about 45 microns; The characteristics of a cathode layer supporting the SOFC stack obtained from such a powder are advantageously improved;
- La taille maximale de la poudre est inférieure à 200 μιη, voire inférieure à 150 μιη, voire inférieure à 110 μιη ;  - The maximum size of the powder is less than 200 μιη, or even less than 150 μιη, or even less than 110 μιη;
- La distribution du facteur de forme R de la poudre est telle que : o moins de 90 %, voire moins de 80 % des particules de la poudre présentent un facteur de forme R supérieur à 1,5, et/ou - The distribution of the form factor R of the powder is such that: less than 90% or even less than 80% of the particles of the powder have a form factor R greater than 1.5, and / or
o plus de 10 %, voire plus de 20 %, et/ou moins de 60 %, voire moins de 40 % des particules de la poudre présentent un facteur de forme R supérieur à 2, et/ou  o more than 10% or even more than 20%, and / or less than 60% or even less than 40% of the particles of the powder have a form factor R greater than 2, and / or
o plus de 5 %, voire plus de 10 %, et/ou moins de 40 %, voire moins de 20 % des particules de la poudre présentent un facteur de forme R supérieur à 2,5, et/ou  o more than 5% or even more than 10%, and / or less than 40% or even less than 20% of the particles of the powder have a form factor R greater than 2.5, and / or
o plus de 2 %, voire plus de 5 %, et/ou moins de 20 %, voire moins de 10 % des particules de la poudre présentent un facteur de forme R supérieur à 3, les pourcentages étant des pourcentages en nombre, le facteur de forme d'une particule étant le rapport L/W entre la longueur L et la largeur W de ladite particule ;  o more than 2% or more than 5%, and / or less than 20% or even less than 10% of the powder particles have a form factor R greater than 3, the percentages being percentages by number, the factor the shape of a particle being the ratio L / W between the length L and the width W of said particle;
- Les particules de la poudre sont des particules broyées, c'est-à-dire résultant d'une opération de broyage d'un produit fondu, par exemple sous la forme de particules plus grosses ou de blocs. Un tel broyage confère une forme particulière aux particules broyées.  - The particles of the powder are ground particles, that is to say resulting from a grinding operation of a molten product, for example in the form of larger particles or blocks. Such grinding gives a particular shape to the ground particles.
L'invention concerne aussi une préforme ou « pièce crue » obtenue par mise en forme d'une poudre selon l'invention, un produit fritté obtenu à partir d'une telle préforme, en particulier une pièce frittée ou une couche frittée. La préforme ou le produit fritté peuvent en particulier se présenter sous la forme d'une couche d'épaisseur inférieure à 2 mm, inférieure à 1 mm ou inférieure à 500 μιη. The invention also relates to a preform or "green part" obtained by shaping a powder according to the invention, a sintered product obtained from such a preform, in particular a sintered part or a sintered layer. The preform or the sintered product may in particular be in the form of a layer of thickness less than 2 mm, less than 1 mm or less than 500 μιη.
Le produit fritté peut notamment présenter une porosité totale supérieure à 20%, de préférence comprise entre 25%> et 50%> en volume, de préférence comprise entre 25%> et 45%o en volume  The sintered product may in particular have a total porosity greater than 20%, preferably between 25% and 50% by volume, preferably between 25% and 45% by volume.
La présente invention se rapporte encore à une électrode, en particulier à une cathode, comportant une région, en particulier une cathode fonctionnelle, ladite électrode, en particulier ladite cathode fonctionnelle, étant constituées à partir d'une poudre selon l'invention. L'invention concerne également une cellule élémentaire d'une pile à combustible à oxyde solide comportant une électrode, de préférence une cathode selon l'invention, et une telle pile à combustible. The present invention also relates to an electrode, in particular to a cathode, comprising a region, in particular a functional cathode, said electrode, in particular said functional cathode being constituted from a powder according to the invention. The invention also relates to an elementary cell of a battery solid oxide fuel comprising an electrode, preferably a cathode according to the invention, and such a fuel cell.
L'invention concerne enfin un procédé de fabrication, dit « procédé de fabrication général », comportant les étapes successives suivantes : The invention finally relates to a manufacturing method, called "general manufacturing process", comprising the following successive steps:
a) préparation, par mélange de matières premières particulaires, d'une charge de départ comportant Zr02, un oxyde de manganèse, optionnellement un dopant de la zircone, et/ou un précurseur d'un ou plusieurs de ces constituants ; b) fusion de la charge de départ jusqu'à obtention d'une matière en fusion, c) refroidissement jusqu'à solidification complète de ladite matière en fusion de manière à obtenir un produit fondu comportant un matériau eutectique, d) optionnellement, broyage dudit produit fondu, a) preparing, by mixing particulate raw materials, a feedstock comprising Zr0 2 , a manganese oxide, optionally a zirconia dopant, and / or a precursor of one or more of these constituents; b) melting of the feedstock until a molten material is obtained, c) cooling to complete solidification of said molten material so as to obtain a molten product comprising a eutectic material, d) optionally, grinding said melted product,
e) optionnellement, mise en forme, voire frittage, du produit fondu et éventuellement broyé,  e) optionally, shaping, or even sintering, of the melted and optionally ground product,
les matières premières étant choisies de manière qu'à l'issue de l'étape c), le produit fondu obtenu soit conforme à l'invention, le refroidissement à l'étape c) comportant une mise en contact de la matière en fusion et/ou du produit fondu avec un fluide comportant de l'oxygène. the raw materials being chosen so that at the end of step c), the molten product obtained is in accordance with the invention, the cooling in step c) involving a contacting of the molten material and or the molten product with a fluid comprising oxygen.
De préférence, le four utilisé à l'étape b) est choisi parmi un four par induction, une torche à plasma, un four à arc ou un laser. Preferably, the oven used in step b) is chosen from an induction furnace, a plasma torch, an arc furnace or a laser.
Définitions Definitions
Un produit est classiquement dit « fondu » lorsqu'il est obtenu par un procédé mettant en œuvre une fusion de matières premières sous la forme d'une masse liquide (ou « matière en fusion »), puis une solidification de cette masse liquide par refroidissement.  A product is conventionally called "molten" when it is obtained by a process involving a melting of raw materials in the form of a liquid mass (or "molten material"), then a solidification of this liquid mass by cooling. .
Une masse liquide peut comporter des particules solides, mais en quantité insuffisante pour rigidifïer ladite masse. A liquid mass may comprise solid particles, but in insufficient quantity to stiffen said mass.
On qualifie classiquement d'« eutectique » une structure ou une morphologie obtenue par fusion d'une composition eutectique puis durcissement de la matière en fusion par refroidissement. Le chapitre « Solidification microstructure : Eutectic and peritectic » du document « Fundamentals of Solidification », third édition, W. KURZ and D.J.FISHER,Classically referred to as "eutectic" is a structure or morphology obtained by melting a eutectic composition and then hardening the melt by cooling. The chapter "Solidification microstructure: Eutectic and peritectic" of "Fundamentals of Solidification", third edition, W. KURZ and DJFISHER,
Trans. Tech. Publication Ltd, Switzerland (1989), décrit les structures eutectiques. Trans. Tech. Publication Ltd, Switzerland (1989), describes eutectic structures.
Une structure eutectique peut être de deux types : régulière (normale) ou irrégulière A eutectic structure can be of two types: regular (normal) or irregular
(anormale). (Abnormal).
Une structure régulière peut être en particulier fibreuse (figure 5A) ou lamellaire (figure 5B). A regular structure can be in particular fibrous (Figure 5A) or lamellar (Figure 5B).
La structure régulière du matériau eutectique d'un produit selon l'invention présente de préférence une morphologie fibreuse, dans laquelle il existe une relation cristallographique marquée entre les phases de l'eutectique. En effet, la morphologie fibreuse correspond à une morphologie dans laquelle l'une des phases, sous la forme de fibres, est noyée dans une matrice continue formée par la seconde phase. L'axe des fibres est alors parallèle à la direction de propagation du front de croissance Df (figure 5 A). Une structure fibreuse peut notamment résulter d'un procédé de fabrication par fusion d'un mélange eutectique comportant une étape de solidification à une vitesse supérieure à 0,17 K/s, de préférence supérieure à 1,7 K/s, supérieure à 8,5 K s, supérieure à 17 K/s, supérieure 34 K/s, supérieure à 50 K/s, voire même supérieure à 85 K/s. The regular structure of the eutectic material of a product according to the invention preferably has a fibrous morphology, in which there is a marked crystallographic relationship between the phases of the eutectic. Indeed, the fibrous morphology corresponds to a morphology in which one of the phases, in the form of fibers, is embedded in a continuous matrix formed by the second phase. The axis of the fibers is then parallel to the direction of propagation of the growth front D f (FIG. 5A). A fibrous structure may in particular result from a process for the manufacture by melting of an eutectic mixture comprising a solidification step at a speed greater than 0.17 K / s, preferably greater than 1.7 K / s, greater than 8 , 5 K s, greater than 17 K / s, greater than 34 K / s, greater than 50 K / s, or even greater than 85 K / s.
Une structure eutectique irrégulière ne présente aucune relation entre l'orientation des deux phases, bien que des fibres croissent généralement selon la direction de propagation du front de croissance de l'eutectique (figures 5C et 5D).  An irregular eutectic structure has no relationship between the orientation of the two phases, although fibers generally grow along the direction of propagation of the eutectic growth front (Figures 5C and 5D).
Un « dopant » de la zircone est un cation métallique autre que le cation zirconium, intégré au sein du réseau cristallin de Zr02, le plus souvent en solution solide. Le dopant peut être présent à titre de cation d'insertion et/ou de substitution au sein de la zircone. A "dopant" of zirconia is a metal cation other than the zirconium cation, integrated within the Zr0 2 crystal lattice, most often in solid solution. The dopant may be present as an insertion and / or substitution cation within the zirconia.
Lorsque de la zircone Zr02 est dite « dopée à x% avec un dopant », cela signifie classiquement que, dans ladite la zircone dopée, la quantité de dopant est le pourcentage molaire de cations de dopant sur la base de la quantité totale de cations de dopant et de cations de zirconium. Par exemple, dans une la zircone dopée à 20 mol% d'yttrium (Y), 20% des cations de zirconium sont remplacés par des cations d'yttrium. De même, dans une la zircone dopée à 20 % de scandium (Se) et 1 % de cérium, 21% des cations de zirconium sont remplacés par 20% de cations de scandium et 1% de cations de cérium. « Zr02 », « zircone » et « oxyde de zirconium » sont synonymes. When zirconia Zr0 2 is said to be "doped at x% with a dopant", this conventionally means that, in said doped zirconia, the amount of dopant is the molar percentage of dopant cations on the basis of the total quantity of cations. of dopant and zirconium cations. For example, in a zirconia doped with 20 mol% yttrium (Y), 20% of the zirconium cations are replaced by yttrium cations. Likewise, in a zirconia doped with 20% of scandium (Se) and 1% of cerium, 21% of the zirconium cations are replaced by 20% of scandium cations and 1% of cerium cations. "Zr0 2 ", "zirconia" and "zirconium oxide" are synonymous.
Par (Zr02 + dopant), on entend la somme des teneurs molaires en cations de zirconium et en dopant. Un précurseur de Zr02, de Mn304 ou de dopant est un composé capable de conduire à la formation de ces oxydes ou de ce dopant, respectivement, par un procédé comportant une fusion, puis une solidification par refroidissement. De la zircone dopée avec un dopant ou avec un oxyde dudit dopant est un exemple particulier de précurseur dudit dopant. By (Zr0 2 + dopant) is meant the sum of the molar contents of zirconium cations and dopant. A precursor of Zr0 2 , Mn 3 0 4 or dopant is a compound capable of leading to the formation of these oxides or dopant, respectively, by a process comprising a melting and then a solidification by cooling. Zirconia doped with a dopant or with an oxide of said dopant is a particular example of a precursor of said dopant.
Par « taille d'une particule », on entend la taille d'une particule donnée classiquement par une caractérisation de distribution granulométrique réalisée avec un granulomètre laser. Le granulomètre laser utilisé ici est un Partica LA-950 de la société HORIBA. By "particle size" is meant the size of a particle conventionally given by a particle size distribution characterization performed with a laser granulometer. The laser granulometer used here is a Partica LA-950 from the company HORIBA.
Les percentiles ou « centiles » 10 (D10), 50 (D50), 90 (D90) et 99,5 (D99i5) d'une poudre sont les tailles de particules correspondant aux pourcentages, en masse, de 10 %, 50 %, 90 % et 99,5 % respectivement, sur la courbe de distribution granulométrique cumulée des particules de la poudre, les tailles de particules étant classées par ordre croissant. Par exemple, 10 %, en masse, des particules de la poudre ont une taille inférieure à D10 et 90 % des particules en masse ont une taille supérieure à D10. Les percentiles peuvent être déterminés à l'aide d'une distribution granulométrique réalisée à l'aide d'un granulomètre laser. The percentiles or "percentiles" (D 10 ), 50 (D 50 ), 90 (D 90 ) and 99.5 (D 9 9 15 ) of a powder are the particle sizes corresponding to the percentages, by mass, of 10%, 50%, 90% and 99.5%, respectively, on the cumulative particle size distribution curve of the powder particles, the particle sizes being ranked in ascending order. For example, 10% by weight of the particles of the powder have a size less than D 10 and 90% of the particles by mass have a size greater than D 10 . Percentiles can be determined using a particle size distribution using a laser granulometer.
On appelle « taille maximale » le percentile 99,5 (p99,5) de ladite poudre. The "maximum size" is the 99.5 percentile (p99, 5 ) of said powder.
On appelle « taille médiane » le percentile D50, c'est-à-dire la taille divisant les particules en première et deuxième populations égales en masse, ces première et deuxième populations ne comportant que des particules présentant une taille supérieure, ou inférieure respectivement, à la taille médiane. The so-called "median size" is the percentile D50, that is to say the size dividing the particles into first and second populations equal in mass, these first and second populations comprising only particles having a larger size, or smaller respectively, at the median size.
On appelle « facteur de forme » R le rapport entre la plus grande dimension apparente, ou « longueur » L, et la plus petite dimension apparente, ou « largeur » W, d'une particule. La longueur et la largeur d'une particule sont classiquement évaluées par la méthode suivante. Après avoir prélevé un échantillon représentatif des particules de la poudre, ces particules sont partiellement noyées dans de la résine et subissent un polissage apte à rendre possible une observation en surface polie. Les mesures du facteur de forme sont réalisées à partir d'images de ces surfaces polies, ces images étant acquises avec un Microscope Electronique à Balayage (MEB), en électrons secondaires, avec une tension d'accélération de 10 kV et un grandissement de xlOO (ce qui représente 1 μιη par pixel sur le MEB utilisé). Ces images sont de préférences acquises dans des zones où les particules sont les mieux séparées, afin de faciliter par la suite la détermination du facteur de forme. Sur chaque particule de chaque image sont mesurées la plus grande dimension apparente, appelée longueur L, et la plus petite dimension apparente, appelée W. De préférence, ces dimensions sont mesurées à l'aide d'un logiciel de traitement d'images, comme par exemple VISILOG commercialisé par la société NOESIS. Pour chaque particule, le facteur de forme R = L/W est calculé. The "ratio of shape" R is the ratio between the largest apparent dimension, or "length" L, and the smallest apparent dimension, or "width" W, of a particle. The length and the width of a particle are classically evaluated by the following method. After taking a representative sample of the particles of the powder, these particles are partially embedded in the resin and undergo polishing capable of making possible a polished surface observation. The shape factor measurements are made from images of these polished surfaces, these images being acquired with an electron scanning microscope (SEM), in secondary electrons, with an acceleration voltage of 10 kV and a magnification of x100. (This represents 1 μιη per pixel on the SEM used). These images are of preference acquired in areas where the particles are best separated, in order to subsequently facilitate the determination of the form factor. On each particle of each image are measured the largest apparent dimension, called length L, and the smallest apparent dimension, called W. Preferably, these dimensions are measured using an image processing software, such as for example VISILOG marketed by the company NOESIS. For each particle, the form factor R = L / W is calculated.
Par « impuretés», on entend les constituants inévitables, introduits involontairement et nécessairement avec les matières premières ou résultant de réactions avec ces constituants. Les impuretés ne sont pas des constituants nécessaires, mais seulement tolérés. Par exemple, les composés faisant partie du groupe des oxydes, nitrures, oxynitrures, carbures, oxycarbures, carbonitrures et espèces métalliques de sodium et autres alcalins, fer, vanadium et chrome sont des impuretés si leur présence n'est pas désirée. By "impurities" is meant the inevitable constituents introduced involuntarily and necessarily with the raw materials or resulting from reactions with these constituents. Impurities are not necessary constituents, but only tolerated. For example, the compounds forming part of the group of oxides, nitrides, oxynitrides, carbides, oxycarbides, carbonitrides and metallic species of sodium and other alkalis, iron, vanadium and chromium are impurities if their presence is not desired.
Sauf indication contraire, tous les pourcentages sont des pourcentages molaires.  Unless otherwise indicated, all percentages are molar percentages.
Par « comportant un », il y a lieu de comprendre « comportant au moins un » ou By "comprising a", it is appropriate to include "comprising at least one" or
« comportant un ou plusieurs », sauf indication contraire. "Comprising one or more", unless otherwise indicated.
Brève description des figures Brief description of the figures
D'autres caractéristiques et avantages de l'invention apparaîtront encore à la lecture de la description qui va suivre et à l'examen du dessin annexé dans lequel  Other features and advantages of the invention will become apparent on reading the description which follows and on examining the appended drawing in which
o la figure 1 représente schématiquement en coupe une pile à combustible à oxyde solide (SOFC) ;  FIG. 1 is a diagrammatic sectional view of a solid oxide fuel cell (SOFC);
o les figures 2, 3, et 4 représentent des photographies des produits eutectiques fondus de ZrC"2 dopée à 8 mol% Y2O3 - Mn304 des exemples 2, 3 et 4, respectivement, selon l'invention, prises à l'aide d'un microscope électronique à balayage (MEB) ; o la figure 5 représente des schémas illustrant des morphologies eutectiques régulières (figure 5 A et 5 B) et irrégulières (figure 5C et 5D). FIGS. 2, 3 and 4 represent photographs of the molten eutectic products of ZrC " 2 doped with 8 mol% Y 2 O 3 - Mn 3 0 4 of Examples 2, 3 and 4, respectively, according to the invention, taken using a scanning electron microscope (SEM); FIG. 5 shows diagrams illustrating regular eutectic (FIGS. 5A and 5B) and irregular (FIGS. 5C and 5D) morphologies.
Sur les photographies, la zircone dopée à 16 mol% de Y apparaît de couleur blanche et l'oxyde de manganèse Mn304 apparaît de couleur grise. In the photographs, the zirconia doped with 16 mol% of Y appears in white color and the manganese oxide Mn 3 0 4 appears gray in color.
Description détaillée detailed description
Des procédés de fusion classiques, adaptés pour obtenir la composition et la microstructure souhaitées, permettent de fabriquer des produits fondus selon l'invention, de différentes tailles, par exemple sous la forme de particules ou de blocs.  Conventional melting methods, adapted to obtain the desired composition and microstructure, make it possible to manufacture molten products according to the invention, of different sizes, for example in the form of particles or blocks.
Un produit fondu selon l'invention peut notamment être fabriqué suivant les étapes a) à e). A l'étape a), la charge de départ est adaptée, de manière conventionnelle, pour que le procédé de fabrication conduise, à l'issue de l'étape c), à un produit fondu selon l'invention présentant éventuellement une ou plusieurs des caractéristiques optionnelles décrites ci-dessus. A melted product according to the invention may in particular be manufactured according to steps a) to e). In step a), the feedstock is conventionally adapted so that the manufacturing process leads, at the end of step c), to a molten product according to the invention optionally having one or more optional features described above.
Le dopant peut être ajouté séparément de la zircone dans la charge de départ. On peut également ajouter, dans la charge de départ, de la zircone dopée.  The dopant can be added separately from the zirconia in the feedstock. It is also possible to add, in the starting charge, the doped zirconia.
Les oxydes Zr02, Μη304, Mn203, MnO, les dopants de la zircone et leurs précurseurs constituent de préférence, avec les impuretés, 100% des oxydes de la charge de départ. De préférence, les impuretés sont telles que, en pourcentages molaires sur la base des oxydes de la charge de départ : The oxides Zr0 2 , Μη 3 0 4 , Mn 2 0 3 , MnO, the dopants of the zirconia and their precursors preferably constitute, with the impurities, 100% of the oxides of the feedstock. Preferably, the impurities are such that, in molar percentages based on the oxides of the feedstock:
■ Ce02 < 0,5%, lorsque le dopant n'est pas un mélange de scandium et d'aluminium et/ou de cérium ; et/ou ■ Ce0 2 <0.5%, when the dopant is not a mixture of scandium and aluminum and / or cerium; and or
■ Na20 < 0,5% ; et/ou ■ Na 2 0 <0.5%; and or
■ Fe203 < 1% ; et/ou ■ Fe 2 0 3 <1%; and or
■ A1203 < 0,3%), lorsque le dopant n'est pas un mélange de scandium et d'aluminium et/ou de cérium ; et/ou ■ A1 2 0 3 <0.3%), when the dopant is not a mixture of scandium and aluminum and / or cerium; and or
■ Ti02 < 0,3% ; et/ou ■ Ti0 2 <0.3%; and or
■ CaO < 0,2%), lorsque le dopant ne comporte pas de calcium ; et/ou ■ CaO <0.2%), when the dopant does not contain calcium; and or
■ MgO < 0,2%o, lorsque le dopant ne comporte pas de magnésium. ■ MgO <0.2% o, when the dopant does not contain magnesium.
A l'étape b), on peut notamment utiliser un four par induction, une torche à plasma, un four à arc ou un laser. De préférence, on utilise un four à arc ou à induction. Avantageusement, il est ainsi possible d'obtenir de grandes quantités de produit, de façon industrielle.  In step b), it is possible in particular to use an induction furnace, a plasma torch, an arc furnace or a laser. Preferably, an arc or induction furnace is used. Advantageously, it is thus possible to obtain large quantities of product, industrially.
A l'étape b), la fusion est de préférence effectuée en conditions oxydantes. Les conditions oxydantes à l'étape b) peuvent être maintenues à l'étape c).  In step b), the melting is preferably carried out under oxidizing conditions. The oxidizing conditions in step b) can be maintained in step c).
L'étape c) comporte de préférence une mise en contact de la matière en fusion avec un fluide comportant de l'oxygène. De préférence, le fluide comporte plus de 10%> d'oxygène, plus de 20%> d'oxygène, en volume. De préférence, le fluide est de l'air. Le produit fondu obtenu à l'issue de l'étape c) peut également être mis en contact avec un tel fluide comportant de l'oxygène.  Step c) preferably comprises bringing the molten material into contact with a fluid comprising oxygen. Preferably, the fluid comprises more than 10% oxygen, more than 20% oxygen, by volume. Preferably, the fluid is air. The molten product obtained at the end of step c) can also be brought into contact with such a fluid comprising oxygen.
A l'étape c), la vitesse de refroidissement est de préférence supérieure à 0,17 K/s, de préférence supérieure à 1,7 K/s, voire supérieure à 8,5 K s, voire supérieure à 17 K/s, voire supérieure 34 K/s, voire supérieure à 50 K/s, voire supérieure à 85 K/s. Une telle vitesse de refroidissement, couplée à une mise en contact de la matière en fusion et/ou du produit fondu avec un fluide comportant de l'oxygène, permet avantageusement de maintenir sensiblement constante la teneur en oxyde de manganèse sous la forme Mn304 (pas ou peu de conversion en Mn203). In step c), the cooling rate is preferably greater than 0.17 K / s, preferably greater than 1.7 K / s, or even greater than 8.5 K s, or even greater than 17 K / s , even greater than 34 K / s, or even greater than 50 K / s, or even greater than 85 K / s. Such cooling rate coupled with a contacting of the melt and / or the melt with a fluid comprising oxygen advantageously makes it possible to maintain substantially constant the manganese oxide content in the form Mn 3 0 4 (no or little conversion to Mn 2 0 3 ).
A l'étape d), optionnelle, le produit fondu issu de l'étape c) peut être broyé afin de faciliter l'efficacité des étapes ultérieures. La granulométrie du produit broyé est adaptée en fonction de sa destination. Le cas échéant, les particules broyées subissent une opération de sélection granulométrique, par exemple par tamisage.  In step d), optional, the melt product from step c) can be milled to facilitate the effectiveness of subsequent steps. The granulometry of the crushed product is adapted according to its destination. If necessary, the ground particles undergo a granulometric selection operation, for example by sieving.
Les particules broyées, et éventuellement tamisées, peuvent notamment présenter une taille supérieure à 0,1 μιη, voire supérieure à 1 μιη, voire supérieure à 0,3 μιη, voire supérieure à 0,5 μιη, voire supérieure à 1 μιη, voire supérieure à 15 μιη, voire supérieure à 20 μιη, et/ou inférieure à 6 mm, voire inférieure à 4 mm, voire inférieure à 3 mm, voire inférieure à 70 μιη, voire inférieure à 50 μιη. The crushed particles, and optionally sieved, may in particular have a size greater than 0.1 μιη, or even greater than 1 μιη, or even greater than 0.3 μιη, or even greater than 0.5 μιη, or even greater than 1 μιη, or even greater at 15 μιη, or even greater than 20 μιη, and / or less than 6 mm, or even less than 4 mm, or even less than 3 mm, or even less than 70 μιη, or even less than 50 μιη.
A l'étape e), optionnelle, le produit est mis en forme, notamment afin d'être fritté. Toutes les techniques conventionnelles de mise en forme et de frittage peuvent être utilisées. In step e), optional, the product is shaped, in particular to be sintered. All conventional shaping and sintering techniques can be used.
Dans un mode de réalisation particulier, le frittage est réalisé in situ, c'est-à-dire après que le produit fondu, éventuellement broyé, a été disposé dans sa position de service, par exemple sous la forme d'une couche de cathode. In a particular embodiment, the sintering is carried out in situ, that is to say after the melted product, possibly ground, has been placed in its service position, for example in the form of a cathode layer. .
Un produit selon l'invention peut présenter une porosité totale élevée, typiquement supérieure à 20% et/ou inférieure à 60%. La porosité dudit produit a une grande importance, car les pores sont le siège d'une partie des réactions de catalyse nécessaires au fonctionnement de la pile à combustible. Les pores sont également le moyen de véhiculer un gaz, en général de l'air, au sein de la cathode. A product according to the invention may have a high total porosity, typically greater than 20% and / or less than 60%. The porosity of said product is of great importance because the pores are the seat of part of the catalysis reactions necessary for the operation of the fuel cell. Pores are also the means of conveying a gas, usually air, within the cathode.
L'invention concerne aussi un premier procédé de fabrication particulier comportant les étapes a), b) décrites ci-dessus, et une étape c) comportant les étapes suivantes : The invention also relates to a first particular manufacturing method comprising the steps a), b) described above, and a step c) comprising the following steps:
ci') dispersion de la matière en fusion sous forme de gouttelettes liquides,  (c) dispersion of the melt in the form of liquid droplets,
Ci") solidification de ces gouttelettes liquides par contact avec un fluide comportant de l'oxygène, de manière à obtenir des particules de produit fondu selon l'invention. Par simple adaptation de la composition de la charge de départ, des procédés de dispersion classiques, en particulier par soufflage, centrifugation ou atomisation, permettent ainsi de fabriquer, à partir d'une matière en fusion, des particules en un produit fondu selon l'invention. Ci ") solidification of these liquid droplets by contact with a fluid comprising oxygen, so as to obtain melt particles according to the invention. By simple adaptation of the composition of the feedstock, conventional dispersion processes, in particular by blowing, centrifugation or atomization, thus make it possible to manufacture, from a molten material, particles into a molten product according to the invention. invention.
Un premier procédé de fabrication particulier peut encore comporter une, voire plusieurs, des caractéristiques optionnelles du procédé de fabrication général listées ci-dessus. A first particular manufacturing method may further include one or more of the optional features of the general manufacturing method listed above.
A l'issue de l'étape c), on obtient des billes selon l'invention, en un produit fondu selon l'invention. At the end of step c), beads according to the invention are obtained in a melted product according to the invention.
Dans une autre variante, les étapes de dispersion Ci') et de solidification Ci ") sont sensiblement simultanées, les moyens mis en œuvre pour la dispersion provoquant un refroidissement de la matière en fusion. Par exemple, la dispersion résulte d'un soufflage de gaz comportant de l'oxygène, par exemple de l'air, à travers la matière à fusion, la température dudit gaz étant adaptée à la vitesse de solidification souhaitée.  In another variant, the dispersion steps Ci ') and the solidification Ci ") are substantially simultaneous, the means used for the dispersion causing the melt to cool, for example, the dispersion results from a blowing of gas comprising oxygen, for example air, through the melting material, the temperature of said gas being adapted to the desired solidification rate.
Le contact entre les gouttelettes et le fluide comportant de l'oxygène peut être d'une durée variable. De préférence cependant, on maintient un contact entre les gouttelettes et ce fluide jusqu'à la solidification complète desdites gouttelettes. The contact between the droplets and the fluid comprising oxygen may be of variable duration. Preferably, however, a contact is maintained between the droplets and this fluid until complete solidification of said droplets.
A l'étape ci"), la vitesse de solidification des gouttelettes liquides est de préférence supérieure à 8,5 K/s, voire supérieure à 17 K/s, voire supérieure à 25,5 K/s. L'invention se rapporte encore à un deuxième procédé de fabrication particulier comportant les étapes a) et b) décrites ci-dessus dans le cadre du procédé de fabrication général, et une étape c) comportant les étapes suivantes :  In step c1), the solidification rate of the liquid droplets is preferably greater than 8.5 K / s, or even greater than 17 K / s, or even greater than 25.5 K / s. still to a second particular manufacturing method comprising steps a) and b) described above as part of the general manufacturing process, and a step c) comprising the following steps:
c2') coulage de ladite matière en fusion dans un moule ; c 2 ') pouring said molten material into a mold;
c2") solidification, par refroidissement par un fluide comportant de l'oxygène, de la matière coulée dans le moule jusqu'à obtention d'un bloc au moins en partie, voire totalement, solidifié ; c 2 ") solidification, by cooling with a fluid comprising oxygen, of the material cast in the mold until a block at least partially, or totally, solidified;
c2'") démoulage du bloc. c 2 '") demolding the block.
Ce deuxième procédé de fabrication particulier peut encore comporter une, voire plusieurs, des caractéristiques optionnelles du procédé de fabrication général listées ci- dessus. This second particular manufacturing method may also include one or more of the optional features of the general manufacturing method listed above.
Dans un mode de réalisation particulier, à l'étape c2'), on utilise un moule autorisant un refroidissement rapide. En particulier, il est avantageux d'utiliser un moule apte à former un bloc sous la forme d'une plaque, et, de préférence, un moule tel que décrit dans US 3,993,119. In a particular embodiment, in step c 2 '), a mold is used which allows rapid cooling. In particular, it is advantageous to use a mold capable of forming a block in the form of a plate, and preferably a mold as described in US 3,993,119.
A l'étape c2') et/ou à l'étape c2") et/ou à l'étape c2"') et/ou après l'étape c2"'), on met en contact avec un fluide oxydant ladite matière en fusion et/ou la matière coulée en cours de solidification dans le moule et/ou le bloc démoulé. In step c 2 ') and / or in step c 2 ") and / or in step c 2 "') and / or after step c 2 "'), contact is made with a oxidizing fluid said melt and / or cast material being solidified in the mold and / or the demolded block.
Le fluide comportant de l'oxygène utilisé à l'étape c2') et/ou à l'étape c2") et/ou à l'étape c2"') et/ou après l'étape c2"'), de préférence gazeux, de préférence de l'air, peut être identique. The fluid comprising oxygen used in step c 2 ') and / or in step c 2 ") and / or in step c 2 "') and / or after step c 2 " ), preferably gaseous, preferably air, may be identical.
De préférence, on commence ledit contact avec le fluide comportant de l'oxygène dès le coulage de la matière en fusion dans le moule et jusqu'au démoulage du bloc. De préférence encore, on maintient ledit contact jusqu'à la solidification complète du bloc. Preferably, one begins said contact with the fluid comprising oxygen as soon as the molten material is poured into the mold and until the mold is removed from the mold. More preferably, maintaining said contact until complete solidification of the block.
A l'étape c2"), la vitesse de solidification des gouttelettes liquides est de préférence supérieure à 8,5 K/s, voire supérieure à 17 K/s, voire supérieure à 25,5 K/s. In step c 2 "), the solidification rate of the liquid droplets is preferably greater than 8.5 K / s, or even greater than 17 K / s, or even greater than 25.5 K / s.
A l'étape c2"'), on procède de préférence au démoulage avant solidification complète du bloc. De préférence, on démoule le bloc dès qu'il présente une rigidité suffisante pour conserver sensiblement sa forme. L'effet du contact avec le fluide comportant de l'oxygène est alors augmenté. In step c 2 "'), demolding is preferably carried out before complete solidification of the block, preferably the block is demolded as soon as it has sufficient rigidity to substantially maintain its shape. fluid comprising oxygen is then increased.
Les premier et deuxième procédés particuliers sont des procédés industriels permettant de fabriquer de grandes quantités de produits, avec de bons rendements.  The first and second particular methods are industrial processes for manufacturing large quantities of products, with good yields.
Bien entendu d'autres procédés que ceux décrits ci-dessus pourraient être envisagés pour fabriquer un produit fondu selon l'invention. Of course, other methods than those described above could be envisaged to manufacture a molten product according to the invention.
Une poudre d'un produit fondu selon l'invention peut en particulier être utilisée pour fabriquer un produit poreux selon l'invention, notamment une couche de cathode poreuse et/ou une couche active de cathode poreuse, par exemple en suivant un procédé comportant les étapes successives suivantes : A powder of a melted product according to the invention may in particular be used to manufacture a porous product according to the invention, in particular a porous cathode layer and / or a porous cathode active layer, for example by following a process comprising the successive stages:
A) préparation d'une poudre d'un produit fondu selon l'invention ;  A) preparing a powder of a melted product according to the invention;
B) mise en forme de la poudre préparée à l'étape A) ;  B) shaping the powder prepared in step A);
C) frittage de ladite poudre ainsi mise en forme. La poudre de produit selon l'invention utilisée à l'étape A) peut notamment être fabriquée suivant les étapes a) à f) décrites ci-dessus.  C) sintering of said powder thus shaped. The product powder according to the invention used in step A) may in particular be manufactured according to steps a) to f) described above.
A l'étape B), la poudre peut être déposée sous la forme d'une couche. A l'étape C), la poudre mise en forme est frittée, suivant des techniques de frittage classiques, de préférence par pressage à chaud. In step B), the powder may be deposited in the form of a layer. In step C), the shaped powder is sintered according to conventional sintering techniques, preferably by hot pressing.
Exemples Examples
Les exemples non limitatifs suivants sont donnés dans le but d'illustrer l'invention. The following nonlimiting examples are given for the purpose of illustrating the invention.
Les produits des exemples selon l'invention 2, 3 et 4 ont été obtenus par fusion en zone flottante sous chauffage laser (« Laser floating zone » en anglais), à l'aide d'un laser C02 de puissance 600 Watts. The products of the examples according to the invention 2, 3 and 4 were obtained by melting in a floating zone under laser heating ("Laser floating zone" in English), using a C0 2 laser with a power of 600 Watts.
Les matières premières utilisées sont les suivantes :  The raw materials used are as follows:
- une poudre de zircone dopée à 16 mol% d'yttrium, commercialisée par la société TOSOH sous la dénomination 8YSZ, de taille médiane égale à 0,25 μιη et de pureté égale à 99,9% ; a zirconia powder doped with 16 mol% of yttrium, marketed by the company TOSOH under the name 8YSZ, of median size equal to 0.25 μιη and of purity equal to 99.9%;
une poudre d'oxyde de manganèse MnO, commercialisée par la société Sigma Aldrich sous la dénomination MnO Manganèse (II) oxide powder - 60 Mesh, de pureté égale à 99%.  an MnO manganese oxide powder, sold by Sigma Aldrich under the name MnO Manganese (II) oxide powder - 60 Mesh, of purity equal to 99%.
Les matières premières en poudre sont choisies et leurs quantités adaptées en fonction du produit à fabriquer. Dans le cas présent, le mélange de matières premières consiste en 73 % de MnO et 27% de 8YSZ, en pourcentages en masse. Ces matières premières sont mélangées intimement dans un broyeur à billes. Lors du mélange dans le broyeur à billes, une solution de 5% de PVA et 95% d'eau est ajoutée dans des proportions de 1 ml par 1,5 à 2 g de mélange de poudres. Le mélange ainsi obtenu est mis sous la forme de baguettes par pressage isostatique à froid (« Cold Isostatique pressing » ou « CIP » en anglais) à 200 Mbar pendant 3 à 4 minutes.  The raw materials in powder are chosen and their quantities adapted according to the product to be manufactured. In the present case, the raw material mixture consists of 73% MnO and 27% 8YSZ, in percentages by weight. These raw materials are intimately mixed in a ball mill. When mixing in the ball mill, a solution of 5% PVA and 95% water is added in proportions of 1 ml per 1.5 to 2 g of powder mixture. The mixture thus obtained is put in the form of chopsticks by cold isostatic pressing ("Cold Isostatic pressing" or "CIP" in English) at 200 Mbar for 3 to 4 minutes.
Les baguettes obtenues sont ensuite frittées sous air de la manière suivante :  The rods obtained are then sintered under air as follows:
Montée de la température ambiante à 400°C à 2°C/min ;  Rise from room temperature to 400 ° C at 2 ° C / min;
Palier de 30 minutes à 400°C ;  Bearing 30 minutes at 400 ° C;
Montée de 400°C à 1300°C à 5°C/min ;  Rise from 400 ° C to 1300 ° C at 5 ° C / min;
Palier de 120 minutes à 1300°C ;  Bearing 120 minutes at 1300 ° C;
Descente à température ambiante à 10°C/min.  Descent at room temperature to 10 ° C / min.
Les baguettes ainsi frittées sont ensuite déplacées en translation (sans rotation des baguettes) à travers le faisceau d'un laser réglé à 60W. Elles subissent ainsi une fusion en zone flottante sous chauffage laser, sous air, avec une vitesse de croissance constante comprise entre 50 et 500 mm/h, ce qui correspond à une vitesse de refroidissement comprise entre 8,5 et environ 85 K/s. Après solidification directionnelle, le produit des baguettes est un produit fondu selon l'invention. The rods thus sintered are then moved in translation (without rotation of the rods) through the beam of a laser set at 60W. They thus undergo a fusion in a floating zone under laser heating, under air, with a constant speed of growth. between 50 and 500 mm / h, which corresponds to a cooling rate of between 8.5 and about 85 K / s. After directional solidification, the product of the rods is a melted product according to the invention.
Le produit Lao,58Sro,4Coo,2Feo,803_6 de l'exemple comparatif 1 est le produit décrit dans « Time-dependent performance of mixed-conducting SOFC cathodes », Solid State Ionics, Volume 177, Issues 19-25, p 1965-1968. The Lao product, 58Sro, 4 Coo, 2 Feo, 8 0 3 _ 6 of Comparative Example 1 is the product described in "Time-dependent performance of mixed-conduct SOFC cathodes," Solid State Ionics, Volume 177, Issues 19 -25, p 1965-1968.
Dans les différents exemples selon l'invention, les teneurs en impuretés étaient inférieures à 2%.  In the various examples according to the invention, the content of impurities was less than 2%.
La nature de l'oxyde de manganèse est mise en évidence par diffraction X. Dans les produits des exemples selon l'invention 2, 3 et 4, l'oxyde de manganèse mis en évidence par diffraction X est Μη304. The nature of the manganese oxide is demonstrated by X-ray diffraction. In the products of the examples according to the invention 2, 3 and 4, the X-ray diffracted manganese oxide is Μη 3 0 4 .
Tous les produits des exemples selon l'invention sont constitués, à plus de 99%, en un matériau eutectique.  All the products of the examples according to the invention consist more than 99% of a eutectic material.
Les résultats sont résumés dans le tableau 1 suivant :  The results are summarized in Table 1 below:
Figure imgf000017_0001
Figure imgf000017_0001
* : exemple comparatif  *: comparative example
Vr : vitesse de refroidissement lors de la fabrication du produit fondu  Vr: cooling rate during manufacture of the molten product
Tableau 1  Table 1
Les produits selon les exemples 2, 3 et 4 présentent un coefficient de dilatation thermique à une température inférieure à 1000°C de l'ordre de 10.10 6 K"1, qui est du même ordre de grandeur que celui de la zircone dopée. Par ailleurs, les produits selon l'invention ne forment pas de phase indésirable de SrZr03 lorsqu'ils sont utilisés dans des électrodes de piles SOFC, comme cela est le cas pour le produit selon l'exemple comparatif 1. Plus généralement, ils présentent une réactivité faible vis-à-vis de la zircone dopée qui peut constituer l'électrolyte d'une pile SOFC. Comme cela apparaît clairement à présent, l'invention fournit un nouveau produit fondu comportant un matériau eutectique Zr02 éventuellement dopé : Mn304 parfaitement adapté à la fabrication de piles SOFC. The products according to Examples 2, 3 and 4 have a coefficient of thermal expansion at a temperature below 1000 ° C. of the order of 10 × 10 6 K -1 , which is of the same order of magnitude as that of the doped zirconia. Furthermore, the products according to the invention do not form an undesirable phase of SrZr0 3 when they are used in SOFC cell electrodes, as is the case for the product according to Comparative Example 1. More generally, they present a low reactivity vis-à-vis the doped zirconia which can constitute the electrolyte of a SOFC stack. As it is now clear, the invention provides a new molten product comprising a eutectic material Zr0 2 possibly doped Mn 3 0 4 perfectly suitable for the manufacture of SOFC batteries.
Bien entendu, la présente invention n'est pas limitée aux modes de réalisation décrits, fournis à titre illustratif.  Of course, the present invention is not limited to the embodiments described, provided for illustrative purposes.

Claims

REVENDICATIONS
Produit fondu constitué, pour plus de 50% de sa masse, d'un matériau eutectique présentant une structure eutectique et une composition telle que: A molten product comprising, for more than 50% of its mass, a eutectic material having a eutectic structure and a composition such that:
- (Zr02 + dopant de la zircone optionnel) : 42,5% - 46,5%, - (Zr0 2 + dopant of the optional zirconia): 42.5% - 46.5%,
- Mn304 : 53,5% - 57,5%, Mn 3 O 4 : 53.5% - 57.5%,
en pourcentages molaires sur la base de la somme des teneurs en Zr02, en dopant et en Mn304. in molar percentages based on the sum of the Zr0 2 , dopant and Mn 3 0 4 contents.
Produit selon la revendication précédente, dans lequel ledit matériau eutectique représente plus de 70% de la masse. Product according to the preceding claim, wherein said eutectic material represents more than 70% of the mass.
Produit selon la revendication précédente, dans lequel ledit matériau eutectique représente plus de 90% de la masse. Product according to the preceding claim, wherein said eutectic material represents more than 90% of the mass.
Produit selon l'une quelconque des revendications précédentes, dans lequel la composition dudit matériau eutectique est telle que, pour un total de 100%, en pourcentages molaires sur la base de la somme des teneurs en Zr02, en dopant et en Mn304 ; A product according to any preceding claim, wherein the composition of said eutectic material is such that, for a total of 100%, in molar percentages based on the total content of Zr0 2, dopant and Mn 3 0 4 ;
- (Zr02 + dopant) : 43% - 46%, - (Zr0 2 + dopant): 43% - 46%,
- Mn304 : 54% - 57%. Mn 3 O 4 : 54% - 57%.
Produit selon la revendication immédiatement précédente, dans lequel la composition dudit matériau eutectique est telle que pour un total de 100%), en pourcentages molaires ou la base de la somme des teneurs en Zr02, en dopant et en Mn304 ; Product according to the immediately preceding claim, wherein the composition of said eutectic material is such that for a total of 100%), in molar percentages or the base of the sum of the contents of Zr0 2 , dopant and Mn 3 0 4 ;
- (Zr02 + dopant) : 43,5% - 45,5%, - (Zr0 2 + dopant): 43.5% - 45.5%,
- Mn304 : 54,5% - 56,5%. Mn 3 O 4 : 54.5% - 56.5%.
Produit selon la revendication immédiatement précédente, dans lequel la composition dudit matériau eutectique est telle que pour un total de 100%), en pourcentages molaires ou la base de la somme des teneurs en Zr02, en dopant et en Mn304 ; Product according to the immediately preceding claim, wherein the composition of said eutectic material is such that for a total of 100%), in molar percentages or the base of the sum of the contents of Zr0 2 , dopant and Mn 3 0 4 ;
- (Zr02 + dopant) : 44% - 45%, - (Zr0 2 + dopant): 44% - 45%,
- Mn304 : 55% - 56%. Mn 3 0 4 : 55% - 56%.
Produit selon l'une quelconque des revendications précédentes, dans lequel, dans ledit matériau eutectique, la zircone Zr02 n'est pas dopée ou est dopée avec un élément choisi parmi le cérium, l'yttrium, le magnésium, le calcium, le scandium, l'aluminium et leurs mélanges. A product according to any one of the preceding claims, wherein in said eutectic material zirconia Zr0 2 is not doped or doped with an element selected from cerium, yttrium, magnesium, calcium, scandium, aluminum and mixtures thereof.
8. Produit selon la revendication précédente, dans lequel, dans ledit matériau eutectique, la zircone Zr02 est dopée avec l'yttrium. 8. Product according to the preceding claim, wherein in said eutectic material, zirconia Zr0 2 is doped with yttrium.
9. Produit selon l'une quelconque des revendications précédentes, dans lequel, dans ledit matériau eutectique, la teneur molaire en dopant, sur la base de la somme des teneurs molaires en cations de zirconium et en cations de dopant, est supérieure à 5% et inférieure à 25%. The product according to any of the preceding claims, wherein in said eutectic material, the molar dopant content, based on the sum of the molar contents of zirconium cations and dopant cations, is greater than 5%. and less than 25%.
10. Produit selon l'une quelconque des revendications précédentes, dans lequel, dans ledit matériau eutectique, The product according to any one of the preceding claims, wherein in said eutectic material,
la zircone Zr02 est dopée seulement avec de l'yttrium, la teneur molaire en cations d'yttrium, sur la base de la somme des teneurs molaires en cations de zirconium et en cations d'yttrium, étant supérieure à 5% et inférieure à 22%, ou zirconia Zr0 2 is doped only with yttrium, the molar content of yttrium cations, on the basis of the sum of the molar contents of zirconium cations and yttrium cations, being greater than 5% and less than 22%, or
la zircone Zr02 est dopée seulement avec du scandium, la teneur molaire en cations de scandium, sur la base de la somme des teneurs molaires en cations de zirconium et en cations de scandium, étant supérieure à 14% et inférieure à 22%o, ou the ZrO 2 zirconia is doped only with scandium, the molar content of scandium cations, on the basis of the sum of the molar contents of zirconium cations and scandium cations, being greater than 14% and less than 22% o, or
la zircone Zr02 est dopée seulement avec un mélange de scandium et de cérium, la teneur molaire en cations de scandium, sur la base de la somme des teneurs molaires en cations de zirconium, en cations de scandium et en cations de cérium, étant supérieure à 14% et inférieure à 22%, et la teneur molaire en cations de cérium, sur la base des teneurs molaires en cations de zirconium, en cations de scandium et en cations de cérium, étant supérieure à 0,5%) et inférieure à 1,5%, ou zirconia Zr0 2 is doped only with a mixture of scandium and cerium, the molar content of scandium cations, on the basis of the sum of the molar contents of zirconium cations, scandium cations and cerium cations, being greater at 14% and below 22%, and the molar content of cerium cations, on the basis of the molar contents of zirconium cations, scandium cations and cerium cations, being greater than 0.5%) and less than 1.5%, or
la zircone Zr02 est dopée seulement avec un mélange de scandium et d'aluminium, la teneur molaire en cations de scandium, sur la base de la somme des teneurs molaires en cations de zirconium, en cations de scandium et en cations d'aluminium, étant supérieure à 14% et inférieure à 22%, et la teneur molaire en cations d'aluminium, sur la base des teneurs molaires en cations de zirconium, en cations de scandium et en cations d'aluminium, étant supérieure à 1% et inférieure à 3%. zirconia Zr0 2 is doped only with a mixture of scandium and aluminum, the molar content of scandium cations, on the basis of the sum of the molar contents of zirconium cations, scandium cations and aluminum cations, being greater than 14% and less than 22%, and the molar content of aluminum cations, on the basis of the molar contents in zirconium cations, in scandium cations and aluminum cations, being greater than 1% and less than 3%.
11. Produit selon la revendication précédente, dans lequel, dans ledit matériau eutectique, la teneur molaire en cations d'yttrium, sur la base de la somme des teneurs molaires en cations de zirconium et en cations d'yttrium, est supérieure à 15% et inférieure à 21%. 11. Product according to the preceding claim, wherein, in said eutectic material, the molar content of yttrium cations, on the basis of the sum of the molar contents of zirconium cations and yttrium cations, is greater than 15%. and less than 21%.
12. Produit selon l'une quelconque des revendications précédentes, dans lequel ledit matériau eutectique présente une structure fibreuse. 12. A product according to any one of the preceding claims, wherein said eutectic material has a fibrous structure.
13. Poudre de particules de produit fondu selon l'une quelconque des revendications précédentes. 14. Electrode comportant une région constituée à partir d'une poudre de particules selon la revendication précédente. 13. The powder of molten product particles as claimed in any one of the preceding claims. 14. Electrode comprising a region formed from a particle powder according to the preceding claim.
15. Procédé de fabrication comportant les étapes successives suivantes : 15. Manufacturing process comprising the following successive steps:
a) Préparation, par mélange de matières premières particulaires, d'une charge de départ comportant Zr02, un oxyde de manganèse, optionnellement un dopant de la zircone, et/ou un précurseur d'un ou plusieurs de ces constituants, b) fusion de la charge de départ jusqu'à obtention d'une matière en fusion, c) refroidissement jusqu'à solidification complète de ladite matière en fusion de manière à obtenir un produit fondu comportant un matériau eutectique, d) optionnellement, broyage dudit produit fondu, a) Preparation, by mixing particulate raw materials, of a feedstock comprising Zr0 2 , a manganese oxide, optionally a zirconia dopant, and / or a precursor of one or more of these constituents, b) melting from the feedstock to a molten material, c) cooling to complete solidification of said molten material to obtain a molten product comprising a eutectic material, d) optionally, grinding said molten product,
e) optionnellement mise en forme, voire frittage, du produit fondu, éventuellement broyé,  e) optionally shaping, or even sintering, the melted product, optionally ground,
les matières premières étant choisies de manière qu'à l'issue de l'étape c), le produit fondu obtenu soit conforme à l'une quelconque des revendications 1 à 12, le refroidissement à l'étape c) comportant une mise en contact de la matière en fusion et/ou du produit fondu avec un fluide comportant de l'oxygène.  the raw materials being chosen so that at the end of step c), the molten product obtained is in accordance with any one of claims 1 to 12, the cooling in step c) involving contacting molten material and / or the molten product with a fluid comprising oxygen.
16. Procédé selon la revendication précédente, dans lequel le four utilisé à l'étape b) est choisi parmi un four par induction, une torche à plasma, un four à arc et un laser. 16. The method according to the preceding claim, wherein the oven used in step b) is selected from an induction furnace, a plasma torch, an arc furnace and a laser.
17. Procédé selon l'une quelconque des deux revendications immédiatement précédentes, dans lequel, à l'étape c), la vitesse de refroidissement est supérieure à 0,17 K/s. 17. A method according to any one of the two immediately preceding claims, wherein in step c) the cooling rate is greater than 0.17 K / s.
18. Procédé selon la revendication précédente, dans lequel, à l'étape c), la vitesse de refroidissement est supérieure à 1,7 K/s. 18. The method according to the preceding claim, wherein in step c), the cooling rate is greater than 1.7 K / s.
19. Procédé selon la revendication précédente, dans lequel, à l'étape c), la vitesse de refroidissement est supérieure à 8,5 K/s. 19. Method according to the preceding claim, wherein in step c), the cooling rate is greater than 8.5 K / s.
20. Procédé selon l'une quelconque des trois revendications immédiatement précédentes, dans lequel, à l'étape c), le fluide comportant de l'oxygène comporte plus de 10% d'oxygène en volume. 20. A method according to any one of the three immediately preceding claims, wherein in step c), the fluid comprising oxygen has more than 10% oxygen by volume.
21. Procédé selon la revendication précédente, dans lequel le fluide comportant de l'oxygène est de l'air. 21. Method according to the preceding claim, wherein the fluid comprising oxygen is air.
22. Procédé selon l'une quelconques des revendications 15 à 21, dans lequel l'étape c) comporte les étapes suivantes : 22. The method according to any one of claims 15 to 21, wherein step c) comprises the following steps:
ci') dispersion de la matière en fusion sous forme de gouttelettes liquides,  (c) dispersion of the melt in the form of liquid droplets,
Ci") solidification de ces gouttelettes liquides par contact avec un fluide comportant de l'oxygène, de manière à obtenir des particules fondues.  Ci ") solidification of these liquid droplets by contact with a fluid comprising oxygen, so as to obtain melted particles.
23. Procédé selon l'une quelconques des revendications 15 à 21, dans lequel l'étape c) comporte les étapes suivantes : 23. The method according to any one of claims 15 to 21, wherein step c) comprises the following steps:
c2') coulage de ladite matière en fusion dans un moule ; c 2 ') pouring said molten material into a mold;
c2") solidification, par refroidissement par un fluide comportant de l'oxygène, de la matière coulée dans le moule jusqu'à obtention d'un bloc au moins en partie, voire totalement, solidifié ; c 2 ") solidification, by cooling with a fluid comprising oxygen, of the material cast in the mold until a block at least partially, or totally, solidified;
c2"') démoulage du bloc. c 2 "') demolding the block.
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