CA2010615A1 - Process for making superconducting metal oxide compositions - Google Patents
Process for making superconducting metal oxide compositionsInfo
- Publication number
- CA2010615A1 CA2010615A1 CA002010615A CA2010615A CA2010615A1 CA 2010615 A1 CA2010615 A1 CA 2010615A1 CA 002010615 A CA002010615 A CA 002010615A CA 2010615 A CA2010615 A CA 2010615A CA 2010615 A1 CA2010615 A1 CA 2010615A1
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- Prior art keywords
- solid
- heating
- temperature
- powder
- superconducting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/45—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides
- C04B35/4504—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides containing rare earth oxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G3/00—Compounds of copper
- C01G3/006—Compounds containing, besides copper, two or more other elements, with the exception of oxygen or hydrogen
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/64—Burning or sintering processes
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N60/00—Superconducting devices
- H10N60/01—Manufacture or treatment
- H10N60/0268—Manufacture or treatment of devices comprising copper oxide
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Ceramic Engineering (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Inorganic Chemistry (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Compositions Of Oxide Ceramics (AREA)
- Oxygen, Ozone, And Oxides In General (AREA)
Abstract
TITLE
PROCESS FOR MAKING SUPERCONDUCTING
METAL OXIDE COMPOSITIONS
ABSTRACT
An improved process for preparing superconducting materials.
PROCESS FOR MAKING SUPERCONDUCTING
METAL OXIDE COMPOSITIONS
ABSTRACT
An improved process for preparing superconducting materials.
Description
20:~061S
TITLE
PROCESS FOR MA~ING SUPERCONDUCTING
METAL OXIDE COMPQSITIONS - :
~: " ~ -'' ~ ':
BAC~GROUND OF THE INVENTION ~.
rield of the Invention This invention relates to processes for making supercondu~ting rare earth-cecium-copper-oxygen compositions and precursors thereof.
References Bednorz and Muller, Z. Phys. B64, 189 (1986), disclose a superconducting phase in the La-Ba-Cu-O system with a superconducting transition temperature of about 35 K. The superconducting phase has been identified as the composition La~ x(Ba,Sr,Ca)~CuO~ y with the tetragonal K2NiF4-type structure and with x typically about 0.15 and y indicating oxygen vacancies.
Wu et al., Phys. Rev. Lett. 58, 908 (1987), disclose a superconducting phase in the Y-Ba-Cu-O system with a superconducting transition temperature of about 90 K. Cava et al., Phys. Rev. Lett. 58, 1676 (1987), have identified this superconducting Y-Ba-Cu-O phase to be orthorhombic, distorted, oxygen-deficient perovskite YBa2Cu3Og ~ where ~ is about 2.1 and present the powder x-ray diffraction pattern and lattice parameters.
~ ,: ., .
20106~S
C. Michel et al., Z. Phys. B - .
Condensed Matter 68, 421 (1987), disclose a novel family of superconducting oxides in the Bi-Sr-Cu-O system with composition close to Bi25r2Cu20~6. A pure phase was isolated for the Composition Bi25r2Cu2o7~6. The X-ray diffraction pattern for this material exhibits some similarity with that of perovskite and the electron diffraction pattern shows the perovskite subcell with the orthorhombic cell parameters of a ~ 5.32 A (0.532 nm), b - 26.6 A ~2.66 nm) and c - 48.8 A (4.88 nm). The material made from ultrapure oxides has a superconducting transition with a midpoint of 22 K as determined from resistivity measurements and zero resistance below 14 K. ~he material made from commercial grade oxides has a superconducting transition with ~ ~idpoint of 7 X.
H. Maeda et al., Jpn. J. Appl. Phys.
27, L209 (1988), disclose a superconducting oxide -in the Bi-Sr-Ca-Cu-O system with the composition near BiSrCaCu20x and a superconducting transition temperature of about 105 K.
The commonly assigned application, "Superconducting Metal Oxide Compositions and Process For Making Them", Canadian Serial No.
590,128, filed Feb. 03, 1989, disclo~e superconducting compositions having the nominal formula Bi.Sr~CaeCu30~ wherein a is from about 1 to about 3, b is from about 3/8 to about 4, c is from about 3/16 to about 2 and x ~ ~1.5 a + b ~ c ~ y) where y is from about 2 to about 5, with the pcoviso that b t C iS from about 3/2 to about 5, said compositions having supecconducting transition temperatures of about 70 K or higher.
:- - . :: ,: : .. . : . . , , .: . . ~
It also discLoses the superconducting metal oxide phase having the formula si2sr3 zCa~Cu2O~
wherein z is from about 0.1 to about 0.9, preferably 0.4 to 0.8 and w is greater than zero but less than about 1. M. A. Subramanian et al., Science 239, 1015 (1988) also disclose the Bi2 Sr3 - 2 Ca2 CU2 8 ~ W Superconductor .
Y. Yumada et al., Jpn. J. Appl. Phys.
27, L996 (1988), disclose the substitution of Pb for Bi in the series Bi~ ~PbxSrCaCu2Oy where x - 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1Ø The Tc increases from 75.5 R for x - O, no Pb present, to a maximum of 85.5 K for x - 0.5. Tc decreases for higher Pb content to 76 K for x - 0.7. No superconductivity was observed for the samples with x - 0.9 and x ~
z. Z. Sheng et al., Nature 332, 55 (1988) disclose superconductivity in the Tl-sa-cu-o system in samples which have nominal compositions Tl2sa2Cu3O~ and TlBaCu3O5 5 Both samples are reported to have onset temperatures above 90 K and zero resistance at 81 K.
Z. Z. Sheng et al., Nature 332, 138 (1988) disclose superconductivity in the Tl-Ca-8a-Cu-O system in samples which have nominal compositions~Tl2Ca2BaCu3Og~ with onset of superconductivity at 120 R. ;
R. M. Hazen et al., Phys. Rev. Lett.
60, 1657 (1988), disclose two superconducting phases in the Tl-sa-Ca-Cu-O system, T12 Ba2 Ca2 Cu3 l o and Tl 2 Ba2CaCu2oa ~ both wit onset of superconductivity near 120 K. C. C.
Torardi et al., Science 240, 631 tl988) disclose the preparation of Tl2sa2Ca2Cu3O~0 with an onset of superconductivity of 125 K.
S. s. P. Parkin et al., Phys. Rev.
Lett. 61, 750 (1988), disclose the structuce TlZa2Ca2Cu309~y with transition temperatures up to 110 K.
M. Hervieu et al., J. Solid State Chem.
75, 212 (1988), disclose the oxide TlBa2 CaCu2 ~ _ y -C. C. Torardi et al., Phys. Rev. B 38, 225 (1988), disclose the oxide Tl2Ba2CuO6 with an onset of superconductivity at about 90 X.
The commonly assigned application, "Superconducting Metal Oxide Compositions and Processes For Manufacture and Use", Canadian Serial No. 609,082, filed Aug. 23, 1989, disclose superconducting compositions having the nominal formula Tl.Pb~CabSr~CudO~
wherein a is from about 1/10 to about 3/2, b is fcom ~bout 1 to about 4, c is from about 1 to about 3, d is from about 1 to about 5, e is from about 3jlO to about 1 and x ~ (a + b + c + d ~ e +y) where y is from about 1/2 to about 3. These composition~ have an onset of superconductiv~ty of at least 70 R.
J. M. Lianq et al., Appl. Phys. Lett.
53, 15 ~1988) disclose a composition Tl8a2Ca3Cu~Ox, with an onset of superconductivity at 155 R and a zero resistance at 123 K.
J. Akimitsu et al., Jpn. J. Appl. Phys.
27, L1859 (1988), disclose superconductivity in the Nd-Sr-Ce-Cu-O system with an onset of superconductivity at about 28 K. E. Takayama-Muromachi et al., Jpn. J. Appl. Phys. 27, L2283 (1988), ceport that the superconducting phase has the focmula (Ndo~66ceo~l3ss~o~2os)2cuoy-S All of the superconducting oxides discussed above exhibit hole conduction. In contrast, Y. Tokura et al., Nature 337, 345 (1989~ disclose a superconducting oxide with the formula Ln2_xCex CU04 _y, where Ln is Pr, Nd or Sm, which exhibits electron conducton. The composition with x - 0.15 and y ~ 0.07 has a transition temperature of 24 K. The superconducting materials were synthesized from a mixture of rare earth metal oxides (CeO2, Pr6O1l, Nd2O3, Sm2O3) and CuO. The powder mixture was calcined in air at 950C for 10 hours, pressed into pellets and sintered in air at 1150C for 12 hours. The samples were quenched in air to room temperature and then annealed for 10 hours under reducing conditions - at 1000C in a stream of Ar/O2 gas with the oxygen partial pressure less than 10- 3 atm - and quenched to room temperature in the same atmosphere. Best results were obtained with an oxygen partial pressure of about 8x10-5 atm. ~ ~ -Results obtained when trying to reproduce the solid state reaction described by Y. Tokura et al., Nature 337, 345 (1989), were inconsistent and the portion of the sample exhibiting superconductivity often small. An ;~
object of this invenition is to provide a process which results in readily reproducible results and well-sintered shaped articles.
. _ ........... . _ :
This invention provides a process for preparing the superconducting phase with the formula Ln2 xCex CUO4 y, where Ln is Pr, Nd or Sm, x is from about 0.14 to about 0.16 and y is greater than about 0.06, said process consisting Z0~0615 S essentially of (a) forming an aqueous solution of nitrates of Ln, Ce and Cu with the atomic ratio of Ln:Ce:Cu being (2-x):x:1, (b) removing the aqueous phase from the lG solution thereby obtaining a powder either by evaporation by heating to form a solid, then heating said solid to a temperature of about 400C to about 6S0C and then grinding the solid, --or by spray drying, ~c) heating said powder or a shaped article formed from said powder to a temperature from about 950C to about 1100C in air for about 24 hours to about 48 hours and then quenching to room temperature, ~d) heating the reducible precursor in ;
a reducing atmosphere to a temperature from about 350C to about 1000C for about 12 or more hours and then quenching while still in the reducing atmosphere to room temperature to produce the superconducting phase.
Preferably x is 0.15. ~:
This invention also provides processes for forming precursors to the superconducting phase with the formula Ln2 xCexCuo~ y, where Ln is Pr, Nd or Sm, x is from about 0.14 to about 0.16 and y is greater than about 0.06, the precursors being the precursor powder obtained by practicing steps ~a) and ~b) of the above process and the reducible precursor obtained by practicing steps ~a), ~b) and (c) of the above process.
, ~ . . . -20~0615 S ~RIEF DESCRIPTION OF THE DRAWING
The Figure is a plot o the flux excluded as a function of temperature for a composition prepared by the process of the invention and one prepared by the isolid state reaction of the art.
DETAILED D~SCRIPTION OF THE INVENTION
This invention provides a process for preparing superconducting oxide phases in the rare earth-cerium-copper system, said process consisting essentially of ta~ forming an aqueous solution of nitrates of the rare earth, Ce and Cu with the ~
atomic ratio of rare earth:Ce:Cu being that : :
required by the phase, ~:
(b) removing the aqueous phase from the :
solution thereby obtaining a powder either by ~ ~ :
evaporation by heating to form a solid, then ~.
heating said solid to a temperature of about 400C to about 650C and then grinding the solid, or by spray drying, (c) heating said powder or a shaped article formed from said powder to a temperature :
from about 950C to about 1100C for about 24 hours to about 48 hours and then quenching in air to room temperature,~
(d) heating the reducible precursor in a reducing atmosphere at a tempecature from about 850C to about 1000C for about 12 or more hours and then quenching while still in the reducing atmosphere to room temperature to produce the superconducting phase.
The aqueous solution of nitrates of Ln, Ce and Cu can be prepared by starting with the appropriate nitrate salts. Alternatively, the ~. :
20~0615 aqueous solution of nitrates can be prepared by reacting one or more of the metal oxides such as Ln2O3, CeO2 and CuO with sufficient concentrated nitric acid to convert the metals present to nitrates. Excess concentrated nitric acid can be used to speed the reaction. The amount of concentrated nitric acid used is typically between one and two times the amount needed to convert all the metals present to metal nitrates.
Solids present in the solution can be dissolved by adding additional water or warming the solution.
The solvent can be removed from the solution by boiling to form a solid.
Preferably, the evaporation is carried out slowly. The solid formed is heated to a ' -temperature of about 400C to about 650C. The resulting black solid produced is ground to form a precursor powder. Altecnatively, the solvent can be removed from the solution by spray drying ~' to directly produce a precursor powder.
The precursor powder or a shaped article formed from the precursor powder is heated to a temperaure from about 950C to about 1100C in air for about 24 hours to about 48 hours and then quenched in air to room tempera~ure to form ,a reducible precursor.
The reducible precursor can be converted to the superconducting composition by heating in a reducing atmosphere at a temperature ~ ; , from about 850C to about 1000C for about 12 '~
hours or more and then quenching while still in ' '' ' the reducing atmosphere to produce the ~,~
superconducting phase. Preferably, the reducing ~- ' atmosphere is flowing argon. ~
~ .
This invention also includes a process for forming a precursor to the superconducting phase with the formula Ln2 xCexCuOq y, where Ln is Pr, Nd or Sm, x is from about 0.14 to about 0.16 and y is greater than about 0.06, said process consisting essentially of (a) forming an aqueous solution of nitrates of Ln, Ce and Cu with the atomic ratio of Ln:Ce:Cu being ~2-x):x:l, (b) removing the aqueous phase from the :
solution to obtain a precursor powder either by - ;
evaporation by heating to form a solid, then heating said solid to a temperature of about 400C to about 650C and then grinding the solid, or by spray drying.
This invention also includes a process for forming a reducible precursor to the , -superconducting phase with the formula ~:~
Ln2 ~CexCuO4 y, where Ln is Pr, Nd or Sm, x is -~
from about 0.14 to about 0.16 and y is greater than about 0.06, said process consisting essentially of (a) forming an aqueous solution of nitrates of Ln, Ce and Cu with the atomic ratio of Ln:Ce:Cu being (2-x):x:1, ~b) removing the aqueous phase from the solution to obtain a~precursor powder either by evaporation by heating to form a solid, then heating said solid to a temperature of about 400C to about 650C and then grinding the solid, or by spray drying, (c) heating said precursor powder or a shaped article formed from said precursor powder to a temperature from about 950C to about 1100C
in air for about 24 hours to about 48 hours and then quenching to room temperature to form a reducible precursor.
Superconductivity can be confirmed by observing magnetic flux exclusion, i.e., the Meissner effect. This effect can be measured by the method described in an article by E. Polturak and s. Fisher in Physical Review s, 36, 5586(1987).
The superconducting compositions of this invention can be used ~o conduct current extremely efficiently or to provide a magnetic field for magnetic imaging for medical purposes.
Thus, by cooling the composition in the form of a wire or bar to a temperature below the superconducting transition temperature, (Tc), in a manner well known to those in this field; and init~ating a flow of electrical current, one can obtain such flow without any electrical resistive losses. To provide exceptionally high magnetic fields with minimal power losses, the wire mentioned previously could be wound to form a coil which would be cooled to a temperature below the superconducting transition temperature, i.
e., using liquid helium, before inducing any current into the coil. Such fields can be used ~ -to levitate objects as large as railroad cars. - -These superconducting compositions are also useful in Josephson devices such as S~UIDS tsuperconducting quantum interference devices) and in instruments that are based on the Josephson effect such as high speed sampling circuits and voltage standards.
20~0615 EXAMPLES OF THE INVENTION
EXAMPLE
:
To a beaker containing a mixture consisting of 3.1124 g of Nd2O3, 0.8223 g of (NH4)2Ce~NO3)6 and 0.7954 g of CuO, corresponding to a Nd:Ce:Cu atomic ratio of 1.85:0.15:1, were added 10 mL concentrated nitric acid and 30 mL of water. The mixture was heated to a temperature maintained in the range between 90C and 100C to dissolve the solids. The resulting clear, i.e., ,~
no solids present, green solution was heated to , "
evaporate some solvent and form a syrupy liquid.
The syrupy liquid was transferred to a platinum dish and heated slowly to dryness. The solid precursor formed was heated at a temperature o~
600C for 2 hours. The black solid was removed from the platinum dish and ground in an agate mortar to form a precursor powder. The precu~sor powder was pressed into a pellet, 10 mm in ~' diameter and about 3 mm thick. The pellet was ' ~--~ , heated at 1100C in air for 24 hours and then , quenched to room temperatuce in air. The pellet was then heated in flow~ng argon at 900C for about 24 hours and,then,quenched to room temperature while still in the flowing argon.
The pellet was crushed into powder and the results of flux exclusion measurements are shown in the Figure. It should be noted that the sample is superconducting at 20 K. AlSo shown in the Figure are the results of flux exclusion ~ ,~
measurements on powder prepared as described in the Experiment below by the solid state method of ~ ~ ' the art. The amount of flux exclusion by the 2010~15 sample of the invention is nearly ten times that of the solid state sample, thereby indicating considerably more superconducting phase present in the sample of the invention as compared to the solid state sample.
EXPERIMENT A
A solid state reaction was carried out to prepare marterial with the same composition as that prepared in the Example. A mixed powder was prepared by grinding 12.4496 g of Nd~03, 1.0328 g of CeO2 and 3.1816 g of CuO in an agate mortar.
A portion of this powder was pressed into a pellet, 10 m~ in diameter and about 3 mm thick.
The remaining powder and the pellet were heated at 950C in air for 10 hours. The powder was pressed into a pellet, 10 mm in diameter and about 3 mm thick. soth pellets were heated at llS0C in air for 12 hours. The pellets were quenched in air to room temperature. The pellets ~ ;
~-~ 25 were then heated in flowing argon at 900C for about 24 hours and then quenched to room temperature while still in the flowing argon. ~
~; ~ The pellets were crushed into powders and the flux exclusion measurements showed similar results.
~ -~
: ~ , "-'`~ -:
-
TITLE
PROCESS FOR MA~ING SUPERCONDUCTING
METAL OXIDE COMPQSITIONS - :
~: " ~ -'' ~ ':
BAC~GROUND OF THE INVENTION ~.
rield of the Invention This invention relates to processes for making supercondu~ting rare earth-cecium-copper-oxygen compositions and precursors thereof.
References Bednorz and Muller, Z. Phys. B64, 189 (1986), disclose a superconducting phase in the La-Ba-Cu-O system with a superconducting transition temperature of about 35 K. The superconducting phase has been identified as the composition La~ x(Ba,Sr,Ca)~CuO~ y with the tetragonal K2NiF4-type structure and with x typically about 0.15 and y indicating oxygen vacancies.
Wu et al., Phys. Rev. Lett. 58, 908 (1987), disclose a superconducting phase in the Y-Ba-Cu-O system with a superconducting transition temperature of about 90 K. Cava et al., Phys. Rev. Lett. 58, 1676 (1987), have identified this superconducting Y-Ba-Cu-O phase to be orthorhombic, distorted, oxygen-deficient perovskite YBa2Cu3Og ~ where ~ is about 2.1 and present the powder x-ray diffraction pattern and lattice parameters.
~ ,: ., .
20106~S
C. Michel et al., Z. Phys. B - .
Condensed Matter 68, 421 (1987), disclose a novel family of superconducting oxides in the Bi-Sr-Cu-O system with composition close to Bi25r2Cu20~6. A pure phase was isolated for the Composition Bi25r2Cu2o7~6. The X-ray diffraction pattern for this material exhibits some similarity with that of perovskite and the electron diffraction pattern shows the perovskite subcell with the orthorhombic cell parameters of a ~ 5.32 A (0.532 nm), b - 26.6 A ~2.66 nm) and c - 48.8 A (4.88 nm). The material made from ultrapure oxides has a superconducting transition with a midpoint of 22 K as determined from resistivity measurements and zero resistance below 14 K. ~he material made from commercial grade oxides has a superconducting transition with ~ ~idpoint of 7 X.
H. Maeda et al., Jpn. J. Appl. Phys.
27, L209 (1988), disclose a superconducting oxide -in the Bi-Sr-Ca-Cu-O system with the composition near BiSrCaCu20x and a superconducting transition temperature of about 105 K.
The commonly assigned application, "Superconducting Metal Oxide Compositions and Process For Making Them", Canadian Serial No.
590,128, filed Feb. 03, 1989, disclo~e superconducting compositions having the nominal formula Bi.Sr~CaeCu30~ wherein a is from about 1 to about 3, b is from about 3/8 to about 4, c is from about 3/16 to about 2 and x ~ ~1.5 a + b ~ c ~ y) where y is from about 2 to about 5, with the pcoviso that b t C iS from about 3/2 to about 5, said compositions having supecconducting transition temperatures of about 70 K or higher.
:- - . :: ,: : .. . : . . , , .: . . ~
It also discLoses the superconducting metal oxide phase having the formula si2sr3 zCa~Cu2O~
wherein z is from about 0.1 to about 0.9, preferably 0.4 to 0.8 and w is greater than zero but less than about 1. M. A. Subramanian et al., Science 239, 1015 (1988) also disclose the Bi2 Sr3 - 2 Ca2 CU2 8 ~ W Superconductor .
Y. Yumada et al., Jpn. J. Appl. Phys.
27, L996 (1988), disclose the substitution of Pb for Bi in the series Bi~ ~PbxSrCaCu2Oy where x - 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1Ø The Tc increases from 75.5 R for x - O, no Pb present, to a maximum of 85.5 K for x - 0.5. Tc decreases for higher Pb content to 76 K for x - 0.7. No superconductivity was observed for the samples with x - 0.9 and x ~
z. Z. Sheng et al., Nature 332, 55 (1988) disclose superconductivity in the Tl-sa-cu-o system in samples which have nominal compositions Tl2sa2Cu3O~ and TlBaCu3O5 5 Both samples are reported to have onset temperatures above 90 K and zero resistance at 81 K.
Z. Z. Sheng et al., Nature 332, 138 (1988) disclose superconductivity in the Tl-Ca-8a-Cu-O system in samples which have nominal compositions~Tl2Ca2BaCu3Og~ with onset of superconductivity at 120 R. ;
R. M. Hazen et al., Phys. Rev. Lett.
60, 1657 (1988), disclose two superconducting phases in the Tl-sa-Ca-Cu-O system, T12 Ba2 Ca2 Cu3 l o and Tl 2 Ba2CaCu2oa ~ both wit onset of superconductivity near 120 K. C. C.
Torardi et al., Science 240, 631 tl988) disclose the preparation of Tl2sa2Ca2Cu3O~0 with an onset of superconductivity of 125 K.
S. s. P. Parkin et al., Phys. Rev.
Lett. 61, 750 (1988), disclose the structuce TlZa2Ca2Cu309~y with transition temperatures up to 110 K.
M. Hervieu et al., J. Solid State Chem.
75, 212 (1988), disclose the oxide TlBa2 CaCu2 ~ _ y -C. C. Torardi et al., Phys. Rev. B 38, 225 (1988), disclose the oxide Tl2Ba2CuO6 with an onset of superconductivity at about 90 X.
The commonly assigned application, "Superconducting Metal Oxide Compositions and Processes For Manufacture and Use", Canadian Serial No. 609,082, filed Aug. 23, 1989, disclose superconducting compositions having the nominal formula Tl.Pb~CabSr~CudO~
wherein a is from about 1/10 to about 3/2, b is fcom ~bout 1 to about 4, c is from about 1 to about 3, d is from about 1 to about 5, e is from about 3jlO to about 1 and x ~ (a + b + c + d ~ e +y) where y is from about 1/2 to about 3. These composition~ have an onset of superconductiv~ty of at least 70 R.
J. M. Lianq et al., Appl. Phys. Lett.
53, 15 ~1988) disclose a composition Tl8a2Ca3Cu~Ox, with an onset of superconductivity at 155 R and a zero resistance at 123 K.
J. Akimitsu et al., Jpn. J. Appl. Phys.
27, L1859 (1988), disclose superconductivity in the Nd-Sr-Ce-Cu-O system with an onset of superconductivity at about 28 K. E. Takayama-Muromachi et al., Jpn. J. Appl. Phys. 27, L2283 (1988), ceport that the superconducting phase has the focmula (Ndo~66ceo~l3ss~o~2os)2cuoy-S All of the superconducting oxides discussed above exhibit hole conduction. In contrast, Y. Tokura et al., Nature 337, 345 (1989~ disclose a superconducting oxide with the formula Ln2_xCex CU04 _y, where Ln is Pr, Nd or Sm, which exhibits electron conducton. The composition with x - 0.15 and y ~ 0.07 has a transition temperature of 24 K. The superconducting materials were synthesized from a mixture of rare earth metal oxides (CeO2, Pr6O1l, Nd2O3, Sm2O3) and CuO. The powder mixture was calcined in air at 950C for 10 hours, pressed into pellets and sintered in air at 1150C for 12 hours. The samples were quenched in air to room temperature and then annealed for 10 hours under reducing conditions - at 1000C in a stream of Ar/O2 gas with the oxygen partial pressure less than 10- 3 atm - and quenched to room temperature in the same atmosphere. Best results were obtained with an oxygen partial pressure of about 8x10-5 atm. ~ ~ -Results obtained when trying to reproduce the solid state reaction described by Y. Tokura et al., Nature 337, 345 (1989), were inconsistent and the portion of the sample exhibiting superconductivity often small. An ;~
object of this invenition is to provide a process which results in readily reproducible results and well-sintered shaped articles.
. _ ........... . _ :
This invention provides a process for preparing the superconducting phase with the formula Ln2 xCex CUO4 y, where Ln is Pr, Nd or Sm, x is from about 0.14 to about 0.16 and y is greater than about 0.06, said process consisting Z0~0615 S essentially of (a) forming an aqueous solution of nitrates of Ln, Ce and Cu with the atomic ratio of Ln:Ce:Cu being (2-x):x:1, (b) removing the aqueous phase from the lG solution thereby obtaining a powder either by evaporation by heating to form a solid, then heating said solid to a temperature of about 400C to about 6S0C and then grinding the solid, --or by spray drying, ~c) heating said powder or a shaped article formed from said powder to a temperature from about 950C to about 1100C in air for about 24 hours to about 48 hours and then quenching to room temperature, ~d) heating the reducible precursor in ;
a reducing atmosphere to a temperature from about 350C to about 1000C for about 12 or more hours and then quenching while still in the reducing atmosphere to room temperature to produce the superconducting phase.
Preferably x is 0.15. ~:
This invention also provides processes for forming precursors to the superconducting phase with the formula Ln2 xCexCuo~ y, where Ln is Pr, Nd or Sm, x is from about 0.14 to about 0.16 and y is greater than about 0.06, the precursors being the precursor powder obtained by practicing steps ~a) and ~b) of the above process and the reducible precursor obtained by practicing steps ~a), ~b) and (c) of the above process.
, ~ . . . -20~0615 S ~RIEF DESCRIPTION OF THE DRAWING
The Figure is a plot o the flux excluded as a function of temperature for a composition prepared by the process of the invention and one prepared by the isolid state reaction of the art.
DETAILED D~SCRIPTION OF THE INVENTION
This invention provides a process for preparing superconducting oxide phases in the rare earth-cerium-copper system, said process consisting essentially of ta~ forming an aqueous solution of nitrates of the rare earth, Ce and Cu with the ~
atomic ratio of rare earth:Ce:Cu being that : :
required by the phase, ~:
(b) removing the aqueous phase from the :
solution thereby obtaining a powder either by ~ ~ :
evaporation by heating to form a solid, then ~.
heating said solid to a temperature of about 400C to about 650C and then grinding the solid, or by spray drying, (c) heating said powder or a shaped article formed from said powder to a temperature :
from about 950C to about 1100C for about 24 hours to about 48 hours and then quenching in air to room temperature,~
(d) heating the reducible precursor in a reducing atmosphere at a tempecature from about 850C to about 1000C for about 12 or more hours and then quenching while still in the reducing atmosphere to room temperature to produce the superconducting phase.
The aqueous solution of nitrates of Ln, Ce and Cu can be prepared by starting with the appropriate nitrate salts. Alternatively, the ~. :
20~0615 aqueous solution of nitrates can be prepared by reacting one or more of the metal oxides such as Ln2O3, CeO2 and CuO with sufficient concentrated nitric acid to convert the metals present to nitrates. Excess concentrated nitric acid can be used to speed the reaction. The amount of concentrated nitric acid used is typically between one and two times the amount needed to convert all the metals present to metal nitrates.
Solids present in the solution can be dissolved by adding additional water or warming the solution.
The solvent can be removed from the solution by boiling to form a solid.
Preferably, the evaporation is carried out slowly. The solid formed is heated to a ' -temperature of about 400C to about 650C. The resulting black solid produced is ground to form a precursor powder. Altecnatively, the solvent can be removed from the solution by spray drying ~' to directly produce a precursor powder.
The precursor powder or a shaped article formed from the precursor powder is heated to a temperaure from about 950C to about 1100C in air for about 24 hours to about 48 hours and then quenched in air to room tempera~ure to form ,a reducible precursor.
The reducible precursor can be converted to the superconducting composition by heating in a reducing atmosphere at a temperature ~ ; , from about 850C to about 1000C for about 12 '~
hours or more and then quenching while still in ' '' ' the reducing atmosphere to produce the ~,~
superconducting phase. Preferably, the reducing ~- ' atmosphere is flowing argon. ~
~ .
This invention also includes a process for forming a precursor to the superconducting phase with the formula Ln2 xCexCuOq y, where Ln is Pr, Nd or Sm, x is from about 0.14 to about 0.16 and y is greater than about 0.06, said process consisting essentially of (a) forming an aqueous solution of nitrates of Ln, Ce and Cu with the atomic ratio of Ln:Ce:Cu being ~2-x):x:l, (b) removing the aqueous phase from the :
solution to obtain a precursor powder either by - ;
evaporation by heating to form a solid, then heating said solid to a temperature of about 400C to about 650C and then grinding the solid, or by spray drying.
This invention also includes a process for forming a reducible precursor to the , -superconducting phase with the formula ~:~
Ln2 ~CexCuO4 y, where Ln is Pr, Nd or Sm, x is -~
from about 0.14 to about 0.16 and y is greater than about 0.06, said process consisting essentially of (a) forming an aqueous solution of nitrates of Ln, Ce and Cu with the atomic ratio of Ln:Ce:Cu being (2-x):x:1, ~b) removing the aqueous phase from the solution to obtain a~precursor powder either by evaporation by heating to form a solid, then heating said solid to a temperature of about 400C to about 650C and then grinding the solid, or by spray drying, (c) heating said precursor powder or a shaped article formed from said precursor powder to a temperature from about 950C to about 1100C
in air for about 24 hours to about 48 hours and then quenching to room temperature to form a reducible precursor.
Superconductivity can be confirmed by observing magnetic flux exclusion, i.e., the Meissner effect. This effect can be measured by the method described in an article by E. Polturak and s. Fisher in Physical Review s, 36, 5586(1987).
The superconducting compositions of this invention can be used ~o conduct current extremely efficiently or to provide a magnetic field for magnetic imaging for medical purposes.
Thus, by cooling the composition in the form of a wire or bar to a temperature below the superconducting transition temperature, (Tc), in a manner well known to those in this field; and init~ating a flow of electrical current, one can obtain such flow without any electrical resistive losses. To provide exceptionally high magnetic fields with minimal power losses, the wire mentioned previously could be wound to form a coil which would be cooled to a temperature below the superconducting transition temperature, i.
e., using liquid helium, before inducing any current into the coil. Such fields can be used ~ -to levitate objects as large as railroad cars. - -These superconducting compositions are also useful in Josephson devices such as S~UIDS tsuperconducting quantum interference devices) and in instruments that are based on the Josephson effect such as high speed sampling circuits and voltage standards.
20~0615 EXAMPLES OF THE INVENTION
EXAMPLE
:
To a beaker containing a mixture consisting of 3.1124 g of Nd2O3, 0.8223 g of (NH4)2Ce~NO3)6 and 0.7954 g of CuO, corresponding to a Nd:Ce:Cu atomic ratio of 1.85:0.15:1, were added 10 mL concentrated nitric acid and 30 mL of water. The mixture was heated to a temperature maintained in the range between 90C and 100C to dissolve the solids. The resulting clear, i.e., ,~
no solids present, green solution was heated to , "
evaporate some solvent and form a syrupy liquid.
The syrupy liquid was transferred to a platinum dish and heated slowly to dryness. The solid precursor formed was heated at a temperature o~
600C for 2 hours. The black solid was removed from the platinum dish and ground in an agate mortar to form a precursor powder. The precu~sor powder was pressed into a pellet, 10 mm in ~' diameter and about 3 mm thick. The pellet was ' ~--~ , heated at 1100C in air for 24 hours and then , quenched to room temperatuce in air. The pellet was then heated in flow~ng argon at 900C for about 24 hours and,then,quenched to room temperature while still in the flowing argon.
The pellet was crushed into powder and the results of flux exclusion measurements are shown in the Figure. It should be noted that the sample is superconducting at 20 K. AlSo shown in the Figure are the results of flux exclusion ~ ,~
measurements on powder prepared as described in the Experiment below by the solid state method of ~ ~ ' the art. The amount of flux exclusion by the 2010~15 sample of the invention is nearly ten times that of the solid state sample, thereby indicating considerably more superconducting phase present in the sample of the invention as compared to the solid state sample.
EXPERIMENT A
A solid state reaction was carried out to prepare marterial with the same composition as that prepared in the Example. A mixed powder was prepared by grinding 12.4496 g of Nd~03, 1.0328 g of CeO2 and 3.1816 g of CuO in an agate mortar.
A portion of this powder was pressed into a pellet, 10 m~ in diameter and about 3 mm thick.
The remaining powder and the pellet were heated at 950C in air for 10 hours. The powder was pressed into a pellet, 10 mm in diameter and about 3 mm thick. soth pellets were heated at llS0C in air for 12 hours. The pellets were quenched in air to room temperature. The pellets ~ ;
~-~ 25 were then heated in flowing argon at 900C for about 24 hours and then quenched to room temperature while still in the flowing argon. ~
~; ~ The pellets were crushed into powders and the flux exclusion measurements showed similar results.
~ -~
: ~ , "-'`~ -:
-
Claims (6)
1. A process for preparing a superconducting phase with the formula Ln2-xCexCuO4-y, where Ln is Pr, Nd or Sm, x is from about 0.14 to about 0.16 and y is greater than about 0.06, said process consisting essentially of (a) forming an aqueous solution of nitrates of Ln, Ce and Cu with the atomic ratio of Ln:Ce:Cu being (2-x):x:1, (b) removing the aqueous phase from the solution thereby obtaining a powder either by evaporation by heating to form a solid, then heating said solid to a temperature of about 400°C to about 650°C and then grinding the solid, or by spray drying, (c) heating said powder or a shaped article formed from said powder to a temperature from about 950°C to about 1100°C in air for about 24 hours to about 48 hours and then quenching to room temperature, and (d) heating the reducible precursor in a reducing atmosphere to a temperature from about 850°C to about 1000°C for about 12 or more hours and then quenching while still in the reducing atmosphere to room temperature to produce the superconducting phase.
2. The process of Claim 1 wherein x is about 0.15.
3. The process of Claim 1 wherein the reducing atmosphere consists essentially of argon.
4. The process of claim 1 wherein Ln is Nd.
5. A process for forming a precursor to a superconducting phase with the formula Ln2-xCexCuO4-y, where Ln is Pr, Nd or Sm, x is from about 0.14 to about 0.16 and y is greater than about 0.06, said process consisting essentially of (a) forming an aqueous solution of nitrates of Ln, Ce and Cu with the atomic ratio of Ln:Ce:Cu being (2-x):x:1, and (b) removing the aqueous phase from the solution to obtain the precursor powder either by evaporation by heating to form a solid, then heating said solid to a temperature of about 400°C to about 650°C and then grinding the solid, or by sp ray drying.
6. A process for forming a reducible precursor to the superconducting phase with the formula Ln2-xCexCuO4-y, where Ln is Pr, Nd or Sm, x is from about 0.14 to about 0.16 and y is greater than about 0.06, said process consisting essentially of (a) forming an aqueous solution of nitrates of Ln, Ce and Cu with the atomic ratio of Ln:Ce:Cu being (2-x):x:1, (b) removing the aqueous phase from the solution to obtain the precursor powder either by evaporation by heating to form a solid, then heating said solid to a temperature of about 400°C to about 650°C and then grinding the solid, or by spray drying, and (c) heating the precursor powder or a shaped article formed from the precursor powder to a temperature from about 950°C to about 1100°C
in air for about 24 hours to about 48 hours and then quenching to room temperature to form the reducible precursor.
in air for about 24 hours to about 48 hours and then quenching to room temperature to form the reducible precursor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US31420089A | 1989-02-23 | 1989-02-23 | |
| US314,200 | 1989-02-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2010615A1 true CA2010615A1 (en) | 1990-08-23 |
Family
ID=23218992
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002010615A Abandoned CA2010615A1 (en) | 1989-02-23 | 1990-02-21 | Process for making superconducting metal oxide compositions |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPH04503657A (en) |
| KR (1) | KR920701046A (en) |
| AU (1) | AU5167790A (en) |
| CA (1) | CA2010615A1 (en) |
| WO (1) | WO1990009961A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4202146C2 (en) * | 1992-01-27 | 1993-12-02 | Roth Technik Gmbh | New oxygen sensors based on complex metal oxides |
| JP2021075408A (en) * | 2019-11-05 | 2021-05-20 | セイコーエプソン株式会社 | Producing method of solid composition and functional ceramic |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1398143A (en) * | 1972-07-18 | 1975-06-18 | Square D Co | Electrical contact materials |
| JPS5137918B2 (en) * | 1974-07-10 | 1976-10-19 | ||
| US4231997A (en) * | 1979-04-05 | 1980-11-04 | Engelhard Minerals & Chemicals Corporation | Preparation of rare earth nitrates |
| FR2578240B1 (en) * | 1985-03-01 | 1987-04-17 | Rhone Poulenc Spec Chim | NEODYME TITANATE AND BARIUM TITANATE NEODYME, PROCESSES FOR THEIR PREPARATION AND THEIR APPLICATIONS IN CERAMIC COMPOSITIONS |
| JPS63259927A (en) * | 1987-04-17 | 1988-10-27 | Nippon Telegr & Teleph Corp <Ntt> | Manufacture of thin film of superconductive matter |
| NL8701787A (en) * | 1987-07-29 | 1989-02-16 | Philips Nv | METHOD FOR MANUFACTURING OXIDICALLY SUPER CONDUCTIVE MATERIAL |
-
1990
- 1990-02-20 KR KR1019910700904A patent/KR920701046A/en not_active Application Discontinuation
- 1990-02-20 JP JP2504037A patent/JPH04503657A/en active Pending
- 1990-02-20 AU AU51677/90A patent/AU5167790A/en not_active Abandoned
- 1990-02-20 WO PCT/US1990/000809 patent/WO1990009961A1/en not_active Application Discontinuation
- 1990-02-21 CA CA002010615A patent/CA2010615A1/en not_active Abandoned
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| Publication number | Publication date |
|---|---|
| JPH04503657A (en) | 1992-07-02 |
| AU5167790A (en) | 1990-09-26 |
| WO1990009961A1 (en) | 1990-09-07 |
| KR920701046A (en) | 1992-08-11 |
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