CA1181616A - Inert electrode compositions - Google Patents

Abstract

A B S T R A C T
A metal composition suitable for use as an inert electrode in the electrolytic production of metal from a metal compound dissolved in a molten salt, the composition defined by the formula:

where Z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal having a valence of 1, 2, 3, 4 or 5 and is the same metal or metals wherever Mi is used in the formula; Mj is a metal having a valence of 2, 3, 4 or 5; Xr is at least one of the elements O, F, N, S, C or B; m, p and n are the number of components which comprise Mi, Mj and Xr; FMi, F'Mi or Fxr are the mole fractions of Mi, Mj and Xr and 0 <

Description

This invention relates to the electrolytic pro-duction of metals such as aluminum, lead, magnesium, zinc, zirconium, titanium, silicon and the like, and more p~rticularly it relates to an inert type electrode for use 5 in ~he production of such metals.
When aluminum, for example, is prodllced by elec-trolysis of alumina dissolve~ in molt2n salt using carbon electrodes, carbon dioxide is produced at the anode as a result of the oxygen liberated on the decomposition of the alumina. That is, the oxygen liberated reac~s and cQnsumes the carbon anode. Thus, about 0.33 pounds of carbon must be used for every pound of aluminum produced~ Carbon such as that obtained from petroleum coke is normally used for such electrodes. However, because of the increasing cost of such cokes, it has become necessary to f ind a new material for the electrodes. A desirable new material would be one which would not be consumed and would be resistant to attack by the molten bath. In addition, ~he new material should be capable of providing a high current efficienay, should not affect the purity of metal and should be reasonable with respect to the cost o raw material and with respect to fab*ication.
Numerous efforts have been made to provide an inert eleatrode of the type referred to but apparently with~
out the required degree of success to make it economically feasible. That is, the inert electrodes in the art appear to be reactive to an extent whioh results in contamination ~i U.S. 205, 651 of the metal being produced as well as consumption o-f the electrode. For example, U.S. Patent 4,039,401 reports that extensive investigations were made to find nonconsumable electrodes for molten salt electrolysis of aluminum oxide and that spinel structure oxides or perovskite structure oxides have excellent electronic conductivity at a temperature of 900 to 1000C. exhibit catalytic action for generation of oxygen and exhibit chemical resistance.
Also, in U.S. Patent 3,960,678 there is disclosed a process for operating a cell for the electrolysis of aluminum oxide with one or more anodes, the work-ing surface of which is of ceramic oxide material. However, according to the patent, the process requires a current density above a minimum value to be maintained over the whole anode surface which comes in contact with the molten electrolyte to minimize the corrosion of the anode. Thus, it can be seen that there is a great need for an electrode which is substantially inert or is resistant to attack by molten salts or molten metal to avoid con-tamination and its attendant problems.
According to the present invention, there is provided a metal composition suitable for use as an inert electrode in the electrolytic prod-uction of metal from a metal compound dissolved in a molten salt, the composition defined by the formula:
20~ ~ ( i)FMi ~ ) Mj ~ (Mi) Mi l ~ r x ) i=l j=l i=l r=l K
m p m n where LFM = I; ~F I ~ ~ ~F IM = 1 and ~ Xr xr i=l j=l i=l r=l z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is a metal having a valence of 1, 2, 3, 4 or 5 and is the same ., -` .

metal or metals wherever Mi i-S used in the :Eormula; Mj is a metal having a valence of 2, 3 or ~; Mi and M; being different metals; Xr is at least one of the elements from the group consisting of 0, F, N, S, C and B; m, p and n are the number of components which comprise Mi, Mj and Xr; FM ' F'M ' F'M or FX are the mole fractions of Mi, Mj and X

and 0 ~ ~ F'M ~ 1 when m ~ 1.

The invention also provides a composition for fabricating into an inert electrode for use in the electrolytic production of metal from a metal compound dissolved in a molten salt, the electrode comprising: two metal compounds combined to provide a combination metal compound having a first phase and a second phase, the first phase consisting essen-tially of a composition defined by the formula M(M'yMl )zX~, and the second phase containing one of said metal compounds, in the formula, y i.s a number in the range of 0.1c y ~0.~5 and 0.55~ y ~0.9 and M is a metal having a valence selected from the group consisting of 1, 2, 3, 4 and 5, M' is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M and M' being different metals, z is a number selected from the group consisting of 2, 3 and 4, X is at least one material selected from the group consisting of 0, F, N, S, C and B, and K is a number in the range of 2 to 4.4, the electrode formulated from said composition being highly conductive and being inert with respect to said molten salt.
In another aspect, the invention provides an improved process for the electrolytic production of metal from a metal compound dissolved in a molten salt using an inert electrode, the improvement comprising: electro-lyzing the metal compound using an inert electrode fabricated from two metal oxides combined to provide an anode metal oxide composition wherein one of the t~

two metal oxides is selected from the group consisting of Ni`O, SnO2, ZrO2, ZnO, CoO, MnO, TiO2 and Ta2O5, the composition containing a material having the formula M(M' Ml ) ~ where y is a number in the range of about 0.1C y ~0.4 and 0.6 cy ~0.9, M is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M' is a metal having a valence selected from the group con-sisting of 2, 3, 4 and 5, M and M' being different metals, O is oxygen, z is a number selected from the group consisting of 2, 3 and 4, and K is a number in the range of 2 to 4.4, an anode formulated from said composition being highly conductive and being inert with respect to said molten salt.
The electrode provided by the present invention is highly resistant to attack by materials in an electrolytic cell and is relatively inexpensive to fabricate.
The electrode material of the invention is suitable for use in the production of metal such as alumimlm, lead, magnesium and zinc and the like utilizing electricity. The metal is produced from a metal compound such as its oxide or salt provided in a molten salt. The electrode material is fabricated from at least two metals or metal compounds combined to provide a combination metal compound containing at least one of the group consis-ting of oxide, fluoride, nitride, sulfide, carbide or boride, the conibination metal compound defined by the formula:

( i) M I I ~(Mj)F M ~ (Mi)!"'M}~ ~ X F:~) m p m n Mi 1, ~ F Mj + ~ F M = 1 a~d ~ XxFx = l;
i=l r=l Z is a number in the range of 1.O to 2.2; K is a number in the range of ~ 2 to 4.4; Mi is at least one metal having a valence of 1, 2, 3, 4 or 5 and is the same metal or metals wherever Mi is used in the composition ; Mj iS a metal having a valence of 2, 3, 4 or 5; Xr is at least one of the elements from the gxoup consisting of 0, F, N, S, C, and B; m, p and n refer ~o the number of componen~s which can compri~e i j r; M1J Mi~ F Mj or Fx are the mole fractlons of i j Xr and ~ M ~ 1 except where Mi is Sn, Ti or Zr or when m = 1, nr when Xr is oxygen and K is 3, in which cases O < ~ F' < 1.
~__ Mi When the metal compound is a metal oxide com-prised of at least two metals, the composition may be defined by the formula M(MyMl y)zXK where y is a number less than one and greater than O and M is a matal having a valence of 1,

2, 3, 4 or 5 and Ml is a metal having a valence of 2, 3, 4 or 5, æ is the number 2, 3 or 4, X is at least one of 0, F, N, S, C or B, and K is a number in the range of ~ to 4~4 the composition being highly conductive and being inert with xespect to molten salt.
There is also provided a metal compound as herein ~ x ~

described wherei~ at least one metal powder is dispersed through the combination metal compound Eor purposes of in-creasing its conductivi~y, the rnetal powder comprising Ni, Co, Fe, Cu, Pt, Rh, In, Ir andjor alloys thereof.
In the accompanying drawings:
Figure l is a graph illustrating or exemplifying the change in lattice parameter versus percent metal oxide in excess of the stoichiometric amount.
Figure 2 is a schematic representation of an electrolytic cell showing the inert electrode of the in-vention bei~g testedO
Figure 3 is a micrograph showing an electrode compssition in accordance with the inventlon.
Figure 4 is another micrograph showing powdered copper dispersed in the electrode composition in accordanca with the invention.
An inert electrode suitable or use for the pro-duction of aluminum, for example, must meet certain criteria.
For example, the ~lectrode must have a high level of con-ductivity. Further, it must be resistant to attack by thebath. In addition, it should have a high resistance to oxidation. Other considera~ions include cost and ease o fabrication. That is, the cost must be such as to make the electrode economically feasible. All of these areas are 2S important. For instance, if the electrode is not resistant to attack, then the metal, e.g. aluminum, produced can be contaminatedO Or, if conductivity is too low, then the cost, in terms of energy, become too high. Thus~ it can be seen that these factors are very important in order to have a completely satis~actory electrode.
Accordingly, it has been discovered that when the electrode is fabricated from metal oxides, nitrides, borides, sulfides, carbides or halldes or combinations there-of, it will meet these requirements only if the oxides or the other materials are carefully selected and combined so as to provide a combination having a specific formulation.
That is, it has been found that without the careful selection of the components ancl the combination thereof in contrslled amounts, the electrode will not have satisfactory resistance to attack by bathO
Thus, in accordance with the present invention, an electrode composition is fa~ricated from at least two metals or metal compounds combined to provids a combination metal compound containing at least one of oxide, fluoride, nitride, sulfide, carbide or boride, th~ combination metal compound defined by the formula:

~Mi~PM ~ (Mj)F'M ~ (Mi~F~ Xr~) i=l J =l i=l r=l m p m n Mi i ~ F Mj + ~F M = 1 and ~ XrFX = l;

i=l j=l i=l r-1 Z is a number in the ranga of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal haviny a valence of 1, 2, 3, 4 or 5 and is the same metal or metals whenever Mi is used in the composition; Mj is a metal having a valence of 2, 3, 4 or 5; Xr is at least one of the elements 0, F, N, S, C and B; m, p and n refer to the number of components whlch can comprise Mi, Mj and Xr; FM
F'M ~ F'M or Fx are the mole fractions of Mi, Mj and Xr 20 and ~ ~'M ~ 1 except where Mi is Sn, Ti or Zr or when m = 1, ox when Xr ls oxygen and K is 3, in which cases M i 1.
When Mi is nickel or cobalt, Mj ls iron and X~
is oxygen, a typical compound would be ~N~o 5Co 5~eo 6NiO 2CO 212~ I~ Mi also includes zirconium in addition to the above then a typical compound can be 0.4 0.2 0 4)(Feo~6Nioo2coo~2~2o4~ Or if tin is sub~
stituted for zirconium, a typical compound would b~
0-4 0.2 nO.4)(FeO.6Nio.2Co 2~24 As noted earlier, it is also within the purvlew of tha inv~ntion to use elements in substitution for or in addition to oxygen. For example, if Mi and Mj are nickel and iron, respectively, then fluorine may be added in adclition to oxygen for example to provide a metal oxyfluoride such as ~i(FeO 6Nio 4~2~ It should be no~d that other metals m~y be used and other elements may be used to provide metal oxysulfides, oxynitrides, oxycarbides and oxyborides and the like, all of which are considered to be within the scope of the present invention. The following list is typical of combination compounds in accordance with the invention, the compounds having metals at least two of which must be used in such combination compounds:
0.6 io ~ 4)24; Ni(FeO 6Nio 4)03F; NiLiF ;
V(Mn V 2)~; Ni(Nio 05CO 95)24; (CoO.9 Ool 2 4 20 (SnO 8V0 2)C24; CO~C0 05FeoO95)2 4 0.9 0.1 2 4 0.5 0.4 0.1) e24; (Nio 6Nbo 4)(FeO 6Ni ) ;
(Ni 8Nbo 2)(FaO 6CO 4)24; (Nio 6 0 4 0.6 0.4 2 4 (Nio 6CoO 2Zro.2)(FeO.8 0 2 2 4 (Nio 6Hfo.4)(FeO~6 0-4 7 4 25 (Nio ~CoO 2HfO.4)(Feo 6 004 2 4;
(Nio 4CoO 2Zro 4)(FeO.6 0.4 2 4 (Nio 6CoO lSnO 3)(Feo.7coo.3)2 4 0.6 0.1ZrO.3~(FeO.7Nio 3)24; NiLi2F4;
(NiO 7CGO 3)Li2F4; (~eoo6Nio.4)(Feo.6 0~4 2 4 (Ge 6CoO 4)(FeO 6CoO 4)24; (Nio.gCUo.l~( 0.6 0.4 2 4 (Nio 6ZrO 2Nbo 2)(FeoO7Nlo.3~2 4i (CoO 6ZrO 4)(Feo.7zno.3)2 4 It should be noted that certain of the compounds can have more inertness than others towards molten metal salts and are thus preferrred. In addition, it should be understood that only those combination metal compounds having at least a reasonable degree of inertness with respect to molten salts are of interest with ~7--respect to kheir use for iner~ electrodes~ That i5, rom-pounds clearly not having a suitable level o~ inertness with xespect to molten salt are not consi~ered to be within the purview of the invention In another aspect of the present invention, at least two metals or metal compounds, such as metal oxides, may be combined to provide or contain a combination metal oxide having the formula M(M'yMl y~z~C~ That i5, after selection of the components including metals or metal oxides they are combined in proportions which will result in a composition having ~his formula. For purposes of the present invention, y must be a number le~s than one and greater than zero. It is an important aspect of this in-vention that these limits be strictly adhered toO That is, it is important that y be less than oneO It has been dis-cov~red that metal oxide composition obtained when y was equal to one resulted in an electrode composition which, while having some resistance to at~ack by a molten bath such as is use~ in making aluminum, had generally an un-acceptable level o~ resis~ance. Compositions formulatedwhere y was equal to one were a~tacked by the bath, e.g.
cryolite with alumina dissolved therein, which, of course, results in an unacceptable contaminatlon level of the metal being produced and the need for purification thereof as well as making it necessary to replace the electrode frequently. For example, U.S. Patent 3,960,678 discloses that anodes comprised of Fe2O3 and SnO2, or NlO, or ZnO
resulted in high levels of impurity, e.g. Sn 0.80~, Fe 1.27%, Ni 0.45%, Fe 1.20%, Zn 2.01%, Fe 2.01%, and thus such materials were considered to b~ unsuitable for anodes because of the impurity problem and because th~ an~des were consumed. Thus~ it can be seen that such or similar com~
positions must be avoided. In the subject formula, when y is equal to zero, it also will be seen that a suitable electrode composition is not obtained. Thus, in a preferred aspect of the invention, the value of y should be controlled so as to be a number in ~he ranga of about 0.1 to 0O9 with a suitable range being about 0.3 to 0.7, particularly when the valence of M is selec~ed frQm the yroup consistiny of l, 2, 4 or 5 and M' is 3. If M is co.nprîsed of only two metals, then it must also include two metals throughout the formula~ It should be understood that M may consist of thr~e or more metals; however, in such instances, M does not have to comprise all such me~als throughout the ~ormula.
The value of z should be a numbex in the range of l.0 to 2.2. Also, the value of K should be a number in the range of 2 to 4.4 with a typ.ical value being in the range of 3 to 4.1. That is, for purposes of the presen~ invention, M and M' are formulated .into the electrode composition in nonstoichiometric amounts in accordance with the principles of the invention.
For purposes of the present invention, M is a metal having a valence of 1, 2, 3, 4 or 5 and M' is a metal having a valence of 2, 3, 4 or 5. Normally, in the present invention, M and M' are different metals, combinations of which are set forth hereinbelow for illustration purposes.
While in the electrode composition d~fined by the formula M(M'yMl y)zOK reference has been made mainly to oxides of such compounds, the oxygen component can be replaced or substituted or partially substituted by fluorine, nitrogen, sulfur, carbon or boron. Accordingly, for con~
venience, the composition may be defined by the formula M(M'yM1 y) XK where X can be at least one of the components, including oxygen, referred to immediately above.
It is within the purview of the inven.ion to derive the electrode composition from metals as well as metal oxides. That is~ metals are contemplated as a source of material which will result in the composition of the instant invention. For exampler M and M' can be metals suitable for forming into an alloy, the proportions of which when subjected to oxidation would provide at least a~ the surface a layer containing or comprising a composition defined by the formula M(M'yMl y)zOK~ for example. It will be understood that additional alloying elements may be provided in the alloy for purposes of modifying the char-acteristics o the resulting oxide. Addltlonal el~ments may be added for purposes of changing the electrical con-ductivity or the resistance of the resulting oxide to attack by bath, e.g. molten salt.
Figure 1 illustrates the effect which can be obtained whenever two metal oxides are combined to provide an electrode ccmposition in accordance with the present invention. That is, in order to obtain the compositions suitable for electrodes of the invention, it is necessary, when using two metal oxid~s, to have one of the oxide~ in excess of -the stoichiometric amount. In contrast, when two metal oxides such as ZnO and Fe2O3 are used, the normal stoichiometric equation is as follows:
Fe2O3 -~ ZnO -~ ZnFe2O~
and the resulting compound is considered to be stoichio-metrically balanced. In such equation, the compound ~ormed has a formula which is referred to as a spinel and which, while exhibiting some resistance to bath, e.g. molten salts, does not exhibit an inertness which is satisfactory, as can be seen from U.S. Patent 3,960,678. Consequently, the dis-solution and the corrosion of an electrode made from such material results in contamination of the metal produced and frequent replacement of the electrode which is economically unsatisfactory, as noted earlier. Because of the pxoblems with stoichiometric spinels containing two metal oxides, it can be seen that they are best avoided. In the present invention, compositions having the formula ~(M'yMl ~)zOK
have demonstrated superior inertness to molten salts when compared to such spinels. As noted above, composition in accordance with the inven~ion can be obtained, in the case of metal oxides, by providing one of the oxides in excess, as shown in Figure 1. In the case of an NiO and Fe2O3 system, the NiO or the Fe2O3 may be kept in excess. In a prefexred embodiment, the components are mixed in accoxdance with ths formula to provide a composition which has one of the components in excess up to the maximum solid solution ~ 10 solubility limit, which is represented by points D or E, Figure 1.
While the inventor does not necessaxily wish to be bound by any theory of invention, it i9 believed that the effect of maintaining one of the metal oxides in excess results in the metal a~oms in excess displacing the other metal atoms in the lattice structure. If metal atoms in excess are smaller ~han the other metal atoms, the result is a decrease in the distance between atoms in the structure and hence the decrease in the lattice parameter, as illus-trated by the line A-E in Figure lo It will be understood that in different systems the effect may be to increase the lattice parameter by using an excess of one of the oxides. This effect would be obtained if the siæe of the metal atom in excess was greater than the other atom. An increase of lattice distance is illustrated by the line A-D of Figure lo It should be understood that point A in Figure 1 shows where stoichiometrically balanced com-positions, e.gO spinels or perovskite type structures, are located.
In addition to the above, it is believed that only a certain amount of substitution of one atom or another can take place to provide a composition in accor-dance with the invention. This point is indicated in Figure l at points D or ~, depending on which metal or metal oxide is provided in excess of the stoichiometric amount. The dotted line from D or E to B or C indicates the change in lattice distance, if substitution continued without interruption. When further substitution does not take place, then there is subs~antially no change in the lattice dista~ce, as illustrated by lines D-B' or E-C'.
It can be seen from Figure 1 that lines A~D or A-E represent a composi ion in accordance with the invention~
It will be noted that lines D-B' or E-C' represent an addi-tional material, such as metal oxide, which can be presentin the composition. Thus, another aspect of the invention contemplates a formulation having a first portion or phase --ll--having the formula M(M'yMl )zOK as defined hereinabove and second portion or phase being a material comprised sub-stantially of a metal oxide, for example as shown in Figure

3. Preferably, in this aspect of the invention the com-ponents are mixed in accordance with the ormula to provid2a composition which has one of the compQnents in excess of the maximum solid solution solubility limit. By reference to Figure l, it will be seen that such limit is represented by point D or E. In addition, Figure 3 illustrates a composition in accordance with the formula wherein one of the components has been provided in excess of the maximum solid solubility limit. When metal oxides are used to provide the electrode material and the amount of metal oxide used is in excess of that needed for substitution or in excess of the maximum solid solubiltiy limit~ the com-bination can be repxesented by the formula M~M'yMl y)~OK ~ MO,where the letters in the formula are as defined herein-above and MO represents ~he second phase. When the electrodeformulation is fabricated from two metal oxides, it is preferred that Ihe second phase comprise at least the metal oxide in excess.
Figure 3 ls a micrograph at 400x of an electrode composition in accordance with the invention. From an examination of Figure 3 it will be seen that there are difPrent phases pxesent. A phase referred to as a first phase has a composition in accordance with the formula of the invention. That is, in the micrograph the first phase, denoted or shown as areas which are subs~antially gray, has a composition defined by the formula M(MyMl v~zOK The 5econd phase, shown as dark gray areas, represents the material in excess of that where substitution can be accom-modated in the lattice structure That is, the dark areas of the second phase are represented by the line D-B' or E-C' of Figure l. The darkest areas in the micrograph represent voids in the composition. The composi~ion shown in Figure 3 was formulated from NiO and Fe2O3 wherein 51.7 wt.% NiO was mixed with 48.3 wt.% Fe2O3 to provide a composition consisting essentlally of Ni(FeO 7Nio 3)24 the NiO being approximately 20 wt.% in excess of the stoichiometric amount.
The formulations referred to are important embodiments of the lnvention. That is, the formulations referred to are important in that if a second phase is present, then it should be chosen carefully in order not to adversely affect the properties of the formulation. It i5 important that the first phase should constitute the major part of the formulation and the second phase con-stitute a minor part. From Figure l it can be seen that the percent excess of material, e.g. metal oxide, can detexmine the amount of the second portion.
When the electrode formulation is comprised of first and second phases, as explained above, it is important that the metal oxide pxovided ~o constitute the minor portion be selected carefully. It has been found that better results can be obtained when the second phase has a lattice structure compatible with the first phase.
With respect to the composition having the for-mulae referred to above, Mi should be at least one of Ni, Sn, Zr, Zn, Co, Mn, Ti, Nb, Ta, Li, Fe or Hf. M may also be a metal from this list. When Mi includes Nl and a tetravalent metal such as Sn, Ti or zr, then m > 3~ Mj should be at least one of Fe, V, Cr, Mn, Al, Nb, Ta, Zr, Sn, Zn, Co, Ni, Hf or Y and M' may also be a metal from this list. Preferably, the composition is ormulated from at least two metal oxides of these metals. A preferred composition is formulated from NiO and Fe203. A typical composition using NiO and Fe203 is Ni(Fey=O 7Ni~,=o 3)24 or Nil 6Fel 404. In the Nio and Fe203 system, y c~n ~an from 0.2 to 0.95 and y' from 0.05 to 0.80. Other com-positions which may be formulated in accordance with the present invention include CotFey=O 6Cyl=O ~)2~ where the starting components are Co304 and Fe203a In the Co30 and Fe203 system, y also can range from 0~4 to 0.95 and y' from 0.05 to 0080. In addition to the above, a three ~D.~ 6 component system may be used dependlng to some extent on characteristics desired i~ the final comp(~sltion For example, Fe203, NiO and Co3O4 may be combined in accordance with the invention. Also, Fe~O3, SnO2 and Co3O4 may be S combined to provide a useful composition. From the above, it will be understood that other combinations can be made which are within the purview of the inventionO
With respect to electrodes made from composition in accordance with the invention, it should be understood that there can be varying degrees of inertness~ Tha~ is, inertness in one respect can be defined with respect to metal being produced. For example, even if an electrode does not appreciably change its physical dimensions, it still can be considered to be lacking appropriate inertness if the metal produced contains an unreasonable amsunt of impurities. In the case of aluminum, commercial grade contains about 99. 5 wto ~ aluminum, the remainder impurities.
Accordinsly, an iner~ electrode, as defined with respect to aluminum, is one capable of producing 99.5 wt.~, the remain-der impurities.
Ceramic fabrication procedures well known tothose skilled in the art can be used to fabricate electrodes in accordance with the present invention.
The electrode composi~ion of the present in-vention is particularly suited for use as an anode in analuminum producing cell. In one preferred aspect, the composition is particularly useful as an an~de for a Hall cell in the production of aluminum. That ls, when the anode is used it has been found to have vsry high resistance to bath used in a Hall cell. For example, the electrode com-position has been found to be resistant to attack by cryolite (Na3AlF6) type electrolyte baths where operated at temperatures around 970C. Typically, such baths have weight ratio of NaF to AlF3 in a range of about lol 1 to 1.3:1. Also, the electrode has been found to have out-standing resistance to lower temper cryolite type baths where NaF/AlF3 ratio can be in the range from 0.5 up to -1~
1.1:1. These baths may be operated typically at tem-peratures of about 800 to 850Cs While such a bath may consist only of A12O3, NaF and AlF3, it is p~ssibLe to provide in the bath at least one halide compound of the alkali and alkaline earth metals other than sodium in an amount effective for reducing the operating temperatureD
Suitable alkali and alkaline earth metal halides are LiF, CaF2 and MgF2. In one embodiment~ the bath can contain LiF in an amount between 1 and 15%.
A cell of the type in which anodes having com-positions in accordance with the invention were tested, is shown in Figure 2~ In Figure 2, there is shown an alumina crucible 10 inside a protection crucible 20. Bath 30 is provided in the alumina crucible and a cathode 40 is pro-vided in the bath. An anode 50 having an inert eleatrode also ` in the bath is shown. Means 60 is sho~n for feeding alumina to the bath. The anode-cathode distance 70 is shown. Metal 80 produced during a run is represented on the cathode and on the bottom of the cell.
In certain instances it may be desirable to use a ceramic composi~ion of the pres nt invention as a cladding. That is, in bipolar application, for exampler the electrode of the invention may be a composite with the cathodic side fabricated from carbon or titanium diboride or the like and separated from the anodic side (which is fabricated from ceramic composition of the present in-vantion) by a higher conducting metal such as nickel, nickel-iron alloys,nickel-chromium alloys or stainless steel 5 . When such arrangement is used, then it can be desirable to protect the ends of such c~mposite electrode with an inert nonconducting material such as silicon nitride, silicon oxynitride, boron nitride, silicon aluminum oxynitri~e and the like~ It will be appreciated that intermediate layers of other metals or materials such as copper, cobalt, platinum, indium, molybdenum, or carbides, nitrides, borides and silicates may be used in the composite electrode.

Also, in electrolytic cells, such as Hall cells, claddings of ~he composition of the invention may be pro~
vided on highly conductive members which may then be u~ed as anode. For example, a composition as defined by the formulas referred to hereinabove may be spraved, e.g.
plasma sprayed, onto the conductlve m~mber to provide a coating or cladding thereon. This approach can have the advantage of lowering or reducing th~ l~ngth of the resistance path between the highly conductive member and m~lten salt electrolyte and thereby significantly lowering the overall resistance of the cell. Highly conduative members which may be used in this application can include metals such as stainless steels, nickel, iron-nickel alloys, copper, and the like whose resistance to attack by molten sal~ electr~lyte might be considered inadequate yet whose conductive properties can be considered hiyhly desirable.
Other highly conductive members to which the composition ~f the invention can be applied include, in general~
sintered composition o~ refxactory hard metals including carbon and graphite.
The thickness o the coating applied to the conductive member should be sufficient to protect the member from attack and yet maintained thin enough to avoid unduly high resistances when electrical current is passed therethrough. Conductivity of the coating should be at least 0.01 Ghm cm In another embodiment of the subject invention, it has been discovered that the conductivity of the electrode composition as defined hereinabove can be in-creased significantly by providing in or dispersing there-through at least one of the metals Co, Fe, Ni, Cu, Pt, Rh, In, Ir ar alloys thereof. When the metal is provided in the el~xode composition, the amount should not constitute more than 30 vol.~ metal, with the remainder being tha composition. In a prefPrred embodiment, the metal provided in the composition can rang~ from about 0.1 to 25 vol.%, with suitable amounts being in the range of 1 to about ~ 16-20 vol.%.
When the electrode composition is formul~ted from NiO and Fe2O3, a highly suitable metal for dispersing through th~3 composition is nickel~ In the NiO ar~d Fe203 system, nickel can be present in the range of about 5 ko 30 wt.%, with a preferred amount being in the range of 5 to 15 wt.%. It has been found ~hat the addition of nicke~ ~o this can increase the conductivity of th~ com-position as much as 30 times.
Metals which may be added to the elec rode com-position should have beneficial results in conductivity and yet should not affect the composition adversely with respect ~o resis~ance to molten salts or bath. Such metals which have these characteristics are those which are normally not preferentially oxidized with respect to the electrode composition or ceramic at operating temperatures.
It should be noted that in order to optimi~e the c~nductivity of the metal provided in the electrode com-po~ition, it is important to minimize the amount of oxide that is permi~ted to form on the metal ~uring fabrication.
That is, it ha~ been discovered that during ormulation of the electrode composition and metal compo~ite, there is a tendency for the metal to oxidize. This can interfere with conductivity and is best avoided. The tendency to oxidize has b~en observed for instance in th~ NiO and Fe203 sy~t~m when nickel was being added.
For purposes of combining the electrod com-po~ition and metal, one suitable method includes grinding of the electrode composition, for example, resulting from the NiO and Fe2O3 combination, to a particle size in the range of 25 to 400 mesh (Tyler Series) and providing the metal in a particle size in the range of 100 to 400 mesh (Tyler Series), e.g. powdered nickel or copper, for example~ ~efore combining, it has been discovered that the powdered metal should be treated with a binder such as carbowax. This treatment should be such that particles of the powdered nickel are substantially coa~ed with a wax layer. Upon mixing, the ground electrode composition adheres to the carbowax providing a layer around the metal particles which is believed to prevent the metal particle from oxidizing during fabrication steps such as sintering~
Typically, the electrode composition and powdered metal or metal compound to be added are mixed together, pressed at about 40,000 psi and sintered at about 1300C.
While copper has been noted hereinabove as being useful for greatly increasing the conduc~ivity of electrode compositions, it has been discovered that copper has great utility in compositions for inert electrod~s, such as those of the invention, as a sintering aid. That is, copper has been found to both greatly increase conductivity and to increase the density of electrode composition of the subject invention. The use of powdered copper having a particle size not greater than -10 mesh (Tyler Series) and prererably not greater than -100 mesh (Tyler Series~
can increase the density of an inert electrode composition substantially. For example, the density of the electrode composition shown in Figure 3 was increased from

4.6 grams/cc to 5.25 grams/cc, an increase in density of 14%.
In addition to the subs~antial incrsase in density, it has been discovered that the use of powdered copper in inert electrode compositions has the effect of removing substantially all of th~ voids th~refrom. That is, the us~ o powdered copper în inert electrode com-positions results in such o~sition being substantially void-free. Eliminating voids or providing a substantially void-fr~e inert electrode is important in that it can have the benefit of greatly increasing the electrode'~ ability to withstand the highly corrosive environments in alec-trolytic cellsO This resul~ is obtained by substantially eliminating sites or voids to which bath, e.g. electrolyte with metal oxide dissolved therein, can migrateO The axtent of elimination of voids can be seen by a comparison of Figure 3 (referred to earlier~ and Figure 4 in which copper is shown as a separate white-colored phase. The electrode composit;on shown (at 400x) in Figure 4 was made or fabrica ted from the same ma~erials and with substanti~lly the same procedures as that in Figur~ 3 except powdered copper was added having a par~icle size of -100 mesh (Tyler Series)O Powdered copper was added in an amount which constitutes 5 w~c.% of the composition shown in Fiyure 4. Powdered copper can constitute as much as 30 wt.
of an electrode composition; however, preerably th~ copper content should be in the range of 0.5 to 20~ . It should be noted that Bi2O3 and V2O5 may also be used to increase the density of inert electrode compositions in the same manner as coppert but on a less preferred basis since neither of these compounds significantly improve con-ductivity. Likewise, the addition of nic]cel as noted hereinabove may be used but on a less preferr0d basis since nickel does not appear to significantly aid den-sification. Of course, it will be understood that com-binations of nickel, copper, Bi2O3 and V2O5 may be used to provide densified inert electrode compositions having high levels of conductivity and being substantially free of voids.
The following examples are still further illustrative of the invention.

a~

Example 1 Fe2O3 having a partie]e size of -10n mesh (I'yler Series) was first heated for purposes of removing moisture. Thereafter, 58 grams of the dried Fe2O3 were mixed with 62 grams of NiO also having a partiele size of -100 mesh (Tyler Series). The mixing was carried out for about one-half hour. After mixing, the eombination of oxides was pressed in a mold at room temperature at a pressure of 25,000 psi to produce a bar-shaped electrode having a density of about 4.0 grams/cc. The bar was sintered in air at a temperature of 1125C for 16 hours. The sintered bar was then crushed or ground to a particle size o~ -100 mesh and again pressed at 25,000 psi and sintered at 1400C to provide a bar-shaped eleetrode having a densi'cy of about 4.6 grams/cc.
The eleetrode was tested as an anode in an eleetrolytie cell, as shown in Figure 2. The cell con'cained a bath eomprising 90 wt.% NaF/AlF3 in a 1.1 ratio, 5 wt.% A12O3 and 5 wt.% CaF2 maintained at 9600C. The anode-eathode distanee in 'che eell was 1-1/2 ineh and a platinum wire was used for purposes of connecting the anode to an electrical souree. ~oltage in the eell was about

5 volts and eurrenc density was 6.5 amps/in2. The eell was run for 24 hours and aluminum was eolleeted on the carbon cathode. On analyzing, the aluminum contained 0.03 wt.% Fe and 0.01 wt.% Ni.
At 950C, the conductivity of the anode was about 0.4 (ohn-cm) 1 Example 2 In this example, the anode was fabricated and tested as in Example l, exeept that after NiO/Fe2O3 was first sintered and ground~ to the mixture (having 51.7 wt.% NiO and 48.3 wt.% Fe2O3) `, . !, "`:! ' was added 10% nicke:L powder having a particl.e size of -lO0 mesh (Tyler Series). However, prior to mixing with the NiO/~e2O3 mixture, the nickel powder was first treated with carbowax~ to pro~ide a coating thereof on the nickel particles, the wax being provided for purposes of ensuring that a coating of the NiO/Fe2O3 mixture adhered to the nickel particles. The combinati.on was pressed and sintered as in Example 1 except the sintering and conductivity ~Trade Mark -19a-, measur~ments took place in an argon atmosphere. The cell was run for 17 hours and aluminum collected on the cathode was analy2ed and found to contain 0.15 w~.~ Fe and 0.15 wt.% Ni.
At 95QC., the conductivity of the anode was about 4 5 (Ghm-cm) 1 which is about a tenfold increase over th.e electrode in Example 1.

In this example, the anode was fabricated and treated as in Example 1 except the anode contained 29.73 10 wt.% Nio~ 31.78 wt.~ Fe2O3 and 38.49 wt.% NiF2. This com-position was mixed, calcined at 800C., screened, pressed at 25,000 psi, sintered at 1100C. for 20 hours, crushed to below 100 mesh, pressed at 25,000 psi and sintered at 1300~C.
for 16 hours. The densi~y of the sample was 5.3 grams/cc 15 and electrical conductivity was 0.03 ohm lcm 1 at 960C.
The electrode was tested ior 26 hours at anode in an electrolytic cell. On analy~ing (Ni ~ Fe) impu~ities in alurninum metal produced during the test, it was found that Ni and Fe combined were only 0.2 wt.%.
2Q Example 4 In this example a calcined mixture of 51.7 wt.~
Nio and 48.3 wt.~ Fe2O3 was plasma-sprayed on 446 stainle~s ~teel substrate to provide an oxide coating thickness of 380~m. The stainless steel subs~rate was cylindrical shaped 25 and was provided with a hemispherical bottom porkion to avoid sharp edges in order to facilitate coating. An anode con~ection was made by tapping threads into the stainless steel and screwing in an Ni 200 threaded rod into the substrate. The assembled anode was tested as in Example 1 30 and the run duration was 11 hours. The metal produced contained less than 0.03 wt.% Ni and approximately 0.05 wt.%
Fe and the substrate was not attacked by the bath.
Example 5 In this example, the anode was fahricated as in 35 Example 2 except that 10 wt.% copper powder was added to the mixture containing 51.7 wt.% NiO and 48.3 wt.~ Fe2O3. The combination was pressed and sintered as in Example 2. The addition of copper into this composition increased its conductivity by about eight-fold. The anode was examined and found to contain three phases, as shown in Figure 4.
That is, metallic copper was found to exis-t as a separate 5 phase. The copper-containing ma-terial was run for 23 hours and examination showed that no significant corrosion had occurred and copper in the aluminum produced amounted to approximately 0.27 wt.%. The same anode was run ayain with a fresh bath for another 25 hours. The copper in aluminum 10 produced amounted to 0.18 wt.%. The same anode was run for a third time in a new bath for 12 hours and the aluminum produced contained approximately 0.1~ wt.% Fe, 0.012 wt.%
Cu and 0.027 wt.% Ni~ This result shows that after some conditioning, corrosion or attack of the anode is very 15 small. Further, the analysis demonstrates that an anode of this composition has the capability of producing commercial grade aluminum (99.5 wt.% Al).
Various modifications may be made in the invention without departing from the spirit thereof, or the scope of the claims, and therefore, the exact form shown is to be taken as illustrative only and not in a limiting sense, and it desired that only such limi-tations shall be placed thereon as are imposed by the prior ar-t, or are specifically set forth in the appended claims.

Claims (83)

1. A metal composition suitable for use as an inert electrode in the electrolytic production of metal from a metal compound dissolved in a molten salt, the composition defined by the formula:

where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is a metal having a valence of 1, 2, 3, 4 or 5 and is the same metal or metals wherever Mi is used in the formula; Mj is a metal having a valence of 2, 3 or 4; Mi and Mj being different metals; Xr is at least one of the elements from the group consisting of O, F, N, S, C and B; m, p and n are the number of components which comprise Mi, Mj and Xr;
FMi, F'Mj, F'Mi or FXr are the mole fractions of Mi, Mj and Xr and <1 when m > 1.

2. The composition in accordance with claim 1 wherein Mi has a valence selected from the group consisting of 1, 2, 4 or 5 and Mj has a valence selected from the group consisting of 2 and 3.

3. The composition in accordance with claim 1 wherein Xr is oxygen.

4. The composition in accordance with claim 1 wherein Mi is at least one metal selected from the group consisting of Ni, Sn, Zr, Zn, Co, Mn, Ti, Nb, Ta, Li, Fe and Hf.

5. The composition in accordance with claim 1 wherein Mj is at least one metal selected from the group consisting of Fe, V, Cr, Al, Zn, Co, Ni, Hf and Y.

6. The composition in accordance with claim 1 wherein Mi is at least one metal selected from the group consisting of Ni, Zn, Co, Li and Fe and wherein Mj is at least one metal selected from the group consisting of Fe, Cr and Y.

7. A metal composition for use as an inert electrode in the electrolytic production of metal from a metal compound dissolved in a metal salt, the composition comprising a combina-tion metal compound defined by the formula:

where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal selected from the group consisting of Ni, Zn, Co, Mn, Nb, Ta, Li and Fe and is the same metal or metals wherever Mi is used in the formula for the composition; and Mj is at least one metal selected from the group consisting of Fe, V, Cr, Al, Co, Ni, Hf and Y; Mi and M;
being different metals; Xr is at least one of the elements from the group consisting of 0, F, N, S, C and B; m, p and n are the number of components which comprise Mi, Mj and Xr; FMi, F'Mj, F'Mi or Fxr are the mole fractions of Mi, Mj and Xr and 0 < F'Mi < 1 when m > 1.

8. A metal composition for use as an inert electrode in the electrolytic production of metal from a metal compound dissolved in a metal salt, the composition comprising a combi-nation metal compound defined by the formula:

where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal selected from the group consisting of Ni, Sn, Zr, Zn, Co, Mn, Ti, Nb, Ta, Li, Fe and Hf and is the same metal or metals wherever Mi is used in the formula for the composition; and Mj is at least one metal selected from the group consisting of Fe, V, Cr, Al, Co, Ni, Hf and Y; Mi and Mj being different metals; Xr is at least one of the elements from the group consisting of O, F, N, S, C and B;
m, p and n are the number of components which comprise Mi, Mj and Xr; FMi, F'Mj, F'Mi or Fxr are the mole fractions of Mi, Mj and X4 and O < F'Mi < 1 when m > 1.

9. A metal composition for use as an inert electrode in the electrolytic production of metal from a metal compound dissolved in a metal salt, the composition comprising a combi-nation metal compound defined by the formula:

where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal selected from the group consisting of Ni, Sn, Ti, Zr, Zn, Co, Mn, Nb, Ta, Li, Fe and Hf and is the same metal or metals wherever Mi is used in the formula for the composition; and Mj is at least one metal selected from the group consisting of V, Cr, Al, Co, Ni, Hf and Y; Mi and Mj being different metals; Xr is at least one of the elements from the group consisting of O, F, N, S, C and B; m, p and n are the number of components which comprise Mi, Mj and Xr;
FMi, F'Mj, F'Mi or FXr are the mole fractions of Mi, Mj and Xr and O < F'Mi < 1 when m > 1.

10. A metal composition for use as an inert electrode in the electrolytic production of metal from a metal compound dissolved in a metal salt, the composition comprising a combi-nation metal compound defined by the formula:

where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal selected from the group consisting of Sn, Ti, Zr, Zn, Co, Mn, Nb, Ta, Li, Fe and Hf and is the same metal or metals wherever Mi is used in the formula for the composition; and Mj is at least one metal selected from the group consisting of Fe, V, Cr, Al, Co, Ni, Hf and Y; Mi and Mj being different metals; Xr is at least one of the elements from the group consisting of 0, F, N, S, C and B;
m, p and n are the number of components which comprise Mi, Mj and Xr; FMi, F'Mj, F'Mi or Fxr are the mole fractions of Mi, Mj and Xr and 0< F'Mi < 1 when m > 1.

11. A metal composition for use as an inert electrode in the electrolytic production of metal from a metal. compound dissolved in a metal salt, the composition comprising a combi-nation metal compound defined by the formula:

where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal selected from the group consisting of Ni, Ti, Zr, Sn, Zn, Co, Mn, Nb, Ta, Li, Fe and Hf and is the same metal or metals wherever Mi is used in the formula for the composition; and Mj is at least one metal selected from the group consisting of Fe, V, Cr, Al, Co, Ni, Hf and Y; Mi and Mj being different metals; Xr is at least one of the elements from the group consisting of 0, F, N, S, C and B;
m, p and n are the number of components which comprise Mi, Mj and Xr and m ? 3; FMi, F'Mj, F'Mi or Fxr are the mole fractions of Mi, Mj and Xr and 0 < F'Mi < 1.

12. A metal composition suitable for use as an inert electrode in the electrolytic production of metal from a metal compound dissolved in a molten salt, the composition defined by the formula:

where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is a metal having a valence of 1, 2, 3, 4 or 5 and is the same metal or metals wherever Mi is used in the formula; Mj is a metal having a valence of 2, 3 or 4; Mi and M; being different metals; Xr is at least one of the elements from the group consisting of O, F, N, S, C and B; m, p and n are the number of components which comprise Mi, Mj and Xr;
FMi, F'Mj, F'Mi or Fxr are the mole fractions of Mi, Mj and Xr and 0 < F'Mi < 0.5.

13. The composition in accordance with claim 12 wherein 0 < F'Mi ? 0.4.

14. The composition in accordance with claim 12 wherein 0.5 < F'Mi< 1.

15. The composition in accordance with claim 12 wherein 0.6 ? F'Mi < 1.

16. A metal composition for use as an inert electrode in the electrolytic production of metal from a metal compound dissolved in a metal salt, the composition comprising a combina-tion metal compound defined by the formula:

where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal selected from the group consisting of Ni, Zn, Co, Mn, Nb, Ta, Li and Fe and Mj is at least one metal selected from the group consisting of Fe, V, Cr, Al, Co, Ni, Hf and Y; Mi and Mj being different metals; Xr is at least one of the elements from the group consisting of 0, F, N, S, C and B; m, p and n are the number of components which comprise Mi, Mj and Xr; FMi, F'Mj, F'Mi or Fxr are the mole fractions of Mi, Mj and Xr and 0 ? F'Mi < 0.5.

17. The composition in accordance with claim 16 wherein 0 < F'Mi ? 0.4.

18. The composition in accordance with claim 16 wherein 0.5 < F'Mi < 1.

19. The composition in accordance with claim 16 wherein 0.6 ? F'Mi < 1.

20. A metal composition for use as an inert electrode in the electrolytic production of metal from a metal compound dissolved in a metal salt, the composition comprising a combina-tion metal compound defined by the formula:

where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal selected from the group consisting of Ni, Sn, Zr, Zn, Co, Mn, Ti, Nb, Ta, Li, Fe and Hf and is the same metal or metals wherever Mi is used in the formula for the composition; and Mj is at least one metal selected from the group consisting of Fe, V, Cr, Al, Co, Ni, Hf and Y; Mi and Mj being different metals; Xr is at least one of the elements from the group consisting of O, F, N, S, C and B;
m, p and n are the number of components which comprise Mi, Mj and Xr; FMi, F'Mj, F'Mi or Fxr are the mole fractions of Mi, Mj and Xr and 0 < F'Mi < 0.5.

21. The composition in accordance with claim 20 wherein 0 < F'Mi ? 0.4.

22. The composition in accordance with claim 20 wherein 0.5 < F'Mi < 1.

23. The composition in accordance with claim 20 wherein 0.6 ? F'Mi < 1.

24. A metal composition for use as an inert electrode in the electrolytic production of metal from a metal compound dissolved in a metal salt, the composition comprising a combina-tion metal compound defined by the formula:

where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal selected from the group consisting of Ni, Sn, Ti, Zr, Zn, Co, Mn, Nb, Ta, Li, Fe and Hf and is the same metal or metals wherever Mi is used in the formula for the composition, and Mj is at least one metal selected from the group consisting of V, Cr, Al, Co, Ni, Hf and Y; Mi and M; being different metals; Xr is at least one of the elements from the group consisting of 0, F, N, S, C and B; m, p and n are the number of components which comprise Mi, Mj and Xr;
FMi, F'Mj, F'Mi or Fxr are the mole fractions of Mi, Mj and Xr and 0 < F'Mi < 0.5.

25. The composition in accordance with claim 24 wherein 0 < F'Mi ? 0.4.

26. The composition in accordance with claim 24 wherein 0.5 < F'Mi < 1.

27. The composition in accordance with claim 24 wherein 0.6 ? F'Mi < 1.

28. A metal composition for use as an inert electrode in the electrolytic production of metal from a metal compound dissolved in a metal salt, the composition comprising a combina-tion metal compound defined by the formula:

where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal selected from the group consisting o f Sn, Ti, Zr, Zn, Co, Mn, Nb, Ta, Li, Fe and Hf and is the same metal or metals wherever Mi is used in the formula for the composition; and Mj is at least one metal selected from the group consisting of Fe, V, Cr, Al, Co, Ni, Hf and Y; Mi and Mj being different metals; Xr is at least one of the elements from the group consisting of O, F, N, S, C and B;
m, p and n are the number of components which comprise Mi, Mj and Xr; are the mole fractions of Mi, Mj and Xr and .

29. The composition in accordance with claim 28 wherein .

30. The composition in accordance with claim 28 wherein .

31. The composition in accordance with claim 28 wherein .

32. A metal composition for use as an inert electrode in the electrolytic production of metal from a metal compound dissolved in a metal salt, the composition comprising a combina-tion metal compound defined by the formula:

where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal selected from the group consisting of Ni, Ti, Zr, Sn, Zn, Co, Mn, Nb, Ta, Li, Fe and Hf ; and Mj is at least one metal selected from the group consisting of Fe, V, Cr, Al, Co, Ni, Hf and Y; Mi and Mj being different metals; Xr is at least one of the elements from the group consisting of O, F, N, S, C and B; m, p and n are the number of components which comprise Mi, Mj and Xr and m 3;
are the mole fractions of Mi, Mj and Xr and .

33. The composition in accordance with claim 32 wherein .

34. The composition in accordance with claim 32 wherein .

35. The composition in accordance with claim 32 wherein .

36. A composition for fabricating into an inert electrode for use in the electrolytic production of metal from a metal compound dissolved in a molten salt, the electrode comprising: two metal compounds combined to provide a combination metal compound having a first phase and a second phase, the first phase consisting essentially of a composition defined by the formula M(M'yM1-y)zXK, and the second phase containing one of said metal compounds, in the formula, y is a number in the range of 0.1?y?0.45 and 0.55?y?0.9 and M is a metal having a valence selected from the group consisting of 1, 2, 3, 4 and 5, M' is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M and M' being different metals, z is a number selected from the group consisting of 2, 3 and 4, X is at least one material selected from the group consisting of O, F, N, S, C and B, and K is a number in the range of 2 to 4.4, the electrode formulated from said composi-tion being highly conductive and being inert with respect to said molten salt.

37. The composition in accordance with claim 36 wherein K is in the range of 3.9 to 4.4.

38. The composition in accordance with claim 36 wherein X is oxygen.

39. The composition in accordance with claim 36 wherein the metal compounds are metal oxides.

40. The composition in accordance with claim 36 wherein M is a metal selected from the group consisting of Ni, Sn, Zr, Zn, Co, Mn, Ti, Nb, Ta, Fe, Hf and Li.

41. The composition in accordance with claim 36 wherein M' is a metal selected from the group consisting of Fe, V, Cr, Mn, Al, Nb, Ta, Sn, Zn, Co, Ni, Hf and Y.

42. The composition in accordance with claim 36 wherein M is a metal selected from the group consisting of Ni, Sn, Mn, Ti, Zr and Zn.

43. The composition in accordance with claim 36 wherein M' is a metal selected from the group consisting of Fe, Cr and V.

44. The composition in accordance with claim 36 wherein M is formulated from NiO.

45. The composition in accordance with claim 36 wherein M' is formulated from Fe2O3.

46. The composition in accordance with claim 36 wherein the metal compounds are NiO and Fe2O3.

47. The composition in accordance with claim 36 wherein the metal compounds are SnO2 and Cr2O3.

48. The composition in accordance with claim 36 wherein the metal compounds are Fe2O3 and Co3O4.

49. The composition in accordance with claim 36 wherein the electrode is an anode.

50. A metal oxide composition for use as an inert electrode in the electrolytic production of metal from a metal compound in a molten salt, the electrode comprising: two metal oxides combined to provide a metal oxide composition having a first and second phase, the first phase having the formula M(M'yM1-y)zOK, the second phase having one of said metal oxides, in the formula y is a number from 0.1?y?0.45 and 0.55?y?0.9, O is oxygen, M is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M' is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M
and M' being different metals, z is a number selected from the group consisting of 2, 3 and 4, and K is a number in the range of 3.9 to 4.4, an electrode formulated from said composition being highly conductive and being inert with respect to said molten salt.

51. A metal oxide composition for use as an inert electrode in the electrolytic production of metal from at least one of the metal oxide and metal salt dissolved in a molten salt, the electrode having a composition comprising: two metal oxides which are combined to provide an electrode metal oxide composition having a first phase and a second phase, the first phase consisting essentially of a material having the formula M(M'yM1-y)zOK and the second phase containing one of said metal oxides in the formula, y is a number in the range of 0.1?y?
0.45 and 0.55?y?0.9, O is oxygen, M is a metal selected from the group consisting of Ni, Sn, Zr, Zn, Co, Mn, Ti, Nb and Ta, M' is a metal having a valence selected from the group consist-ing of 2, 3, 4 and 5, M and M' being different metals, z is a number selected from the group consisting of 2, 3 and 4, and-K
is a number in the range of 2 to 4, an electrode formulated from said composition being highly conductive and being inert with respect to said molten salt.

52. In an improved process for the electrolytic production of metal from a metal compound dissolved in a molten salt using an inert electrode, the improvement comprising:
electrolyzing the metal compound using an inert electrode fabricated from two metal compounds combined to provide a combi-nation metal compound consisting essentially of a composition defined by the formula M(M'yM1-y)zXK where y is a number in the range of 0.1?y?0.45 and 0.55?y?0.9, M is a metal having a valence selected from the group consisting of 1, 2, 3, 4 and 5, M' is a metal having a valence selected from the group consist-ing of 2, 3, 4 and 5, M and M' being different metals, z is a number selected from the group consisting of 2, 3 and 4, X is at least one material selected from the group consisting of O, F, N, S, C and B, and K is a number in the range of 2 to 4.4, an electrode formulated from said composition being highly conductive and being inert with respect to said molten salt.

53. The composition in accordance with claim 52 wherein K is in the range of 3.9 to 4.4.

54. The composition in accordance with claim 52 wherein the composition is comprised of a first phase and a second phase, the first phase having the formula of claim 52.

55. The composition in accordance with claim 54 wherein the second phase has the formula MO.

56. The composition in accordance with claim 52 wherein X is oxygen.

57. The composition in accordance with claim 52 wherein the metal compounds are metal oxides.

58. The composition in accordance with claim 52 wherein the metal compounds are metal oxides and the oxides are combined to provide a combination metal oxide having a first phase and a second phase, the first phase consisting essentially of a composition defined by the formula M(M'yM1-y)zOK and the second phase containing at least one of said metal oxides, in the formula, y is a number in the range of 0.1?y?0.45 and 0.55 y?0.9, M is a metal having a valence selected from the group consisting of 1, 2, 3, 4 and 5, M' is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, O is oxygen, z is a number selected from the group consisting of 2, 3 and 4, and K is a number in the range of 2 to 4.4.

59. The composition in accordance with claim 54 wherein the second phase is comprised of at least one of the metal oxides used to provide the electrode composition.

60. The composition in accordance with claim 52 wherein M is a metal selected from the group consisting of Ni, Sn, Zr, Zn, Co, Mn, Ti, Nb, Ta, Fe, Hf and Li.

61. The composition in accordance with claim 52 wherein M' is a metal selected from the group consisting of Fe, V, Cr, Mn, Al, Nb, Ta, Sn, Zn, Co, Ni, Hf and Y.

62. The composition in accordance with claim 52 wherein M is a metal selected from the group consisting of Ni, Sn, Mn, Ti, Zr and Zn.

63. The composition in accordance with claim 52 wherein M' is a metal selected from the group consisting of Fe, Cr and V.

64. The composition in accordance with claim 52 wherein M is formulated from NiO.

65. The composition in accordance with claim 52 wherein M' is formulated from Fe2O3.

66. The composition in accordance with claim 52 wherein the metal compounds are NiO and Fe2O3.

67. The composition in accordance with claim 52 wherein the metal compounds are SnO2 and Cr2O3.

68. The composition in accordance with claim 52 wherein the metal compounds are Fe2O3 and Co3O4.

69. The composition in accordance with claim 52 wherein the metal produced from the metal compound electrolysis is aluminum.

70. The composition in accordance with claim 52 wherein the metal compound dissolved in the molten salt is alumina.

71. The composition in accordance with claim 52 wherein the electrode is an anode.

72. In an improved process for the electrolytic production of metal from a metal compound dissolved in a molten salt using an inert electrode, the improvement comprising:
electrolyzing the metal compound using an inert electrode fabricated from two metal oxides combined to provide an anode metal oxide composition wherein one of the two metal oxides is selected from the group consisting of NiO, SnO2, ZrO2, ZnO, CoO, MnO, TiO2 and Ta2O5, the composition containing a material having the formula M(M'yM1-y)zOK where y is a number in the range of about 0.1?y?0.4 and 0.6?y?0.9, M is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M' is a metal having a valence selected from the group consist-ing of 2, 3, 4 and S, M and M' being different metals, O is oxygen, z is a number selected from the group consisting of 2, 3 and 4, and K is a number in the range of 2 to 4 4, an anode formulated from said composition being highly conductive and being inert with respect to said molten salt.

73. In an improved process for the electrolytic production of metal from a metal compound dissolved in a molten salt using an inert electrode, the improvement comprising:
electrolyzing the metal compound using an inert electrode fabricated from two metal oxides combined to provide an anode metal oxide composition wherein one of the two metal oxides is selected from the group consisting of Fe2O3, Cr2O3, Mn2O3, and Y2O3, the composition containing a material having the formula M(M'yM1-y)zOK where y is a number in the range of 0.1?y?0.4 and 0.6?y?0.9, M is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M' is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M
and M' being two different metals, O is oxygen, z is a number selected from the group consisting of 2, 3 and 4, and K is a number in the range of 2 to 4.4, an anode formulated from said composition being highly conductive and being inert with respect to said molten salt.

74. In an improved process for the electrolytic production of metal from a metal compound dissolved in a molten salt using an inert electrode, the improvement comprising:
electrolyzing the metal compound using an inert electrode fabricated from two metal oxides combined to provide a metal oxide composition wherein one of the two metal oxides is selected from the group consisting of NiO, SnO2, ZrO2, ZnO, CoO, MnO and TiO2, the other metal oxide is selected from the group consisting of Fe2O3, Cr2O3, Mn2O3, and Y2O3, the composition containing a material having the formula M(M'yM1-y)zOK where y is a number in the range of 0.1?y?0.4 and 0.6?y?0.9, M is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M' is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M and M' being two different metals, O is oxygen, z is a number selected from the group consisting of 2, 3 and 4, and K is a number in the range of 2 to 4.4, an anode formulated from said composition being highly conductive and being inert with respect to said molten salt.

75. In an improved process for the electrolytic production of metal from a metal compound dissolved in a molten salt using an inert electrode, the improvement comprising:
electrolyzing the metal compound using an inert electrode fabricated from two metal oxides combined to provide a metal oxide composition having a first and second phase, the first phase having the formula M(M'yM1-y)zOK, the second phase containing one of said metal oxides, in the formula, y is a number from 0.1?y?.45 and 0.55?y?0.9, M is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M' is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M and M' being different metals, O is oxygen, z is a number selected from the group consisting of 2, 3 and 4, and K is a number in the range of 3.9 to 4.4, an electrode formulated from said composition being highly conductive and being inert with respect to said molten salt.

76. In an improved process for the electrolytic production of metal from a metal compound dissolved in a molten salt using an inert electrode, the improvement comprising: two metal oxides which are combined to provide an electrode metal oxide composition having a first phase and a second phase, the first phase consisting essentially of a material having the formula M(M'yM1-y)zOK, the second phase containing one of said metal oxides, in the formula, y is a number in the range of 0.1?
y?0.45 and 0.55?y?0.9, M is a metal selected from the group consisting of Ni, Sn, Zr, Zn, Co, Mn, Ti, Nb and Ta, M' is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M and M' being different metals, O is oxygen, z is a number selected from the group consisting of 2, 3 and 4, and K
is a number in the range of 2 to 4, an electrode formulated from said composition being highly conductive and being inert with respect to said molten salt.

77. A composition suitable for fabricating into an inert electrode for use in the electrolytic production of metal from a metal compound dissolved in a molten salt, the composi-tion comprising: (a) a combination metal compound defined by the formula:
where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal having a valence of 1, 2, 3, 4 or 5 and is the same metal or metals when Mi is used in the composition; Mj is a metal having a valence of 2, 3 or 4; Mi and Mj being different metals; Xr is at least one of the elements from the group consisting of O, F, N, S, C and B;
m, p and n are the number of components which comprise Mi, Mj and Xr; are the mole fractions of Mi, Mj and Xr and ; and (b) at least one metal powder dispersed through the combination metal compound for purposes of increasing its conductivity, the metal powder selected from the group consisting of Ni, Co, Fe, Cu, Pt, Rh, In and Ir and alloys thereof, the metal powder provided in a particle size of not greater than -10 mesh (Tyler Series) for dispersing in the combination metal compound and constituting up to about 30 vol.%
of the composition.

78. The electrode composition in accordance with claim 77 wherein the metal powder is in the range of 0.1 to 25 vol.%.

79. The electrode composition in accordance with claim 77 wherein the metal powder dispersed in the ceramic oxide composition has a particle size not greater than -100 mesh (Tyler Series).

80. The electrode composition in accordance with claim 77 wherein the metal. powder is at least one of the group consisting of Ni and Cu.

81. A composition suitable for fabricating into an inert electrode for use in the electrolytic production of metal from a metal compound dissolved in a molten salt, the electrode comprising: (a) a combination metal compound defined by the formula:
where z is a number in the range of 1.0 to 2.2; K is a number in the range of 2.0 to 4.4; Mi is at least one metal having a valence of 1, 2, 3, 4 or 5 and is the same metal or metals when Mi is used in the composition; Mj is a metal having a valence of 2, 3 or 4; Mi and Mj being different metals; Xr is at least one of the elements from the group consisting of O, F, N, S, C and B;
m, p and n are the number of components which comprise Mi, Mj and Xr; are the mole fractions of Mi, Mj and Xr and ; and (b) at least one metal powder dispersed through the combination metal compound for purposes of increasing its conductivity, the metal powder selected from the group consisting of Ni, Cu and Fe and alloys thereof, and provided in a particle size of not greater than -10 mesh (Tyler Series) for dispersing in the combination metal compound and constituting 0.1 to 25 vol.% of the inert electrode composition.

82. A composition suitable for fabricating into an inert electrode for use in the electrolytic production of metal from metal compound dissolved in a molten salt, the electrode comprising: (a) at least two metal compounds combined to provide a combination metal compound consisting essentially of a composition defined by the formula M(M'yM1-y)zXK where y is a number less than one and greater than 0 and M is a metal having a valence selected from the group consisting of 1, 2, 3, 4 and 5 and M' is a metal having a valence selected from the group consisting of 2, 3, 4 and 5, M and M' being different metals, z is a number selected from the group consisting of 2, 3 and 4, X
is at least one material selected from the group consisting of O, F, N, S, C and B, and K is a number in the range of 2 to 4.4, the electrode being highly conductive and being inert with respect to said molten salt; and (b) at least one metal powder dispersed through the combination metal compound for purposes of increasing its conductivity, the metal powder selected from the group consisting of Ni, Co, Fe, Cu, Pt, Rh, In and Ir, and alloys thereof, the metal powder provided in a particle size of not greater than -10 mesh (Tyler Series) for dispersing in the combination metal compound and constituting up to about 20 vol.%
of the composition.

83. The composition in accordance with claim 82 wherein X is oxygen.