US 5,686,198 AGranted

Low cost stable air electrode material for high temperature solid oxide electrolyte electrochemical cells

AssigneeWestinghouse Electric Corp.

InventorsLewis J. H. Kuo, Prabhakar Singh, Roswell J. Ruka, Theodore R. Vasilow, Raymond J. Bratton

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Abstract

A low cost, lanthanide-substituted, dimensionally and thermally stable, gas permeable, electrically conductive, porous ceramic air electrode composition of lanthanide-substituted doped lanthanum manganite is provided which is used as the cathode in high temperature, solid oxide electrolyte fuel cells and generators. The air electrode composition of this invention has a much lower fabrication cost as a result of using a lower cost lanthanide mixture, either a natural mixture or an unfinished lanthanide concentrate obtained from a natural mixture subjected to incomplete purification, as the raw material in place of part or all of the higher cost individual lanthanum. The mixed lanthanide primarily contains a mixture of at least La, Ce, Pr, and Nd, or at least La, Ce, Pr, Nd and Sm in its lanthanide content, but can also include minor amounts of other lanthanides and trace impurities. The use of lanthanides in place of some or all of the lanthanum also increases the dimensional stability of the air electrode. This low cost air electrode can be fabricated as a cathode for use in high temperature, solid oxide fuel cells and generators.

Claims22

Dependent claims

A method of making a lanthanide-substituted, dimensionally and thermally stable, electrically conductive, porous ceramic air electrode structure, which comprises:

(a) providing powdered oxides or carbonates of a natural lanthanide mixture comprising at least two lanthanides from the group of La, Ce, Pr, Nd, and Sm;
(b) providing powdered oxides or carbonates of individual species of La and Mn, at least one A-site dopant from the group of individual species of Ca, Sr, Ba, and Ce, and, at least one B-site dopant from the group of individual species of Mg, Ni, Cr, Al and Fe;
(c) blending together said powdered oxides or carbonates of the lanthanide mixture with said powdered oxides or carbonates of said individual species of La and Mn, said at least one A-site dopant from the group of individual species of Ca, Sr, Ba, and Ce, and, said at least one B-site dopant from the group of individual species of Mg, Ni, Cr, Al and Fe, in appropriate proportions to provide a lanthanide-substituted doped LaMnO.sub.3 composition after calcining;
(d) pressing the blended powder into a shape;
(e) calcining the pressed shape at a temperature of from about 1,300.degree. C. to 1,750.degree. C. for about 1 to 5 hours;
(f) pulverizing the calcined shape to powder form;
(g) blending the calcined powder with at least one from the group of a cohesion agent, a pore-forming agent, a water-soluble binder, a wetting agent, and water to provide a formable mixture, where the calcined powder constitutes from about 90% to 95% by weight of the formable mixture;
(h) molding the formable composition into a shaped air electrode structure;
and
(i) sintering the shaped air electrode structure in air at a temperature from about 1,300.degree. C. to 1,750.degree. for about 1 to 6 hours, to form a porous, shaped, air electrode structure of the lanthanide-substituted doped LaMnO.sub.3 composition.

7 more elements

Dependencies are inferred from the claim text.