Sr- and Ni-doped LaCoO{sub 3} and LaFeO{sub 3} perovskites: New cathode materials for solid-oxide fuel cells
- Univ. of Texas, Austin, TX (United States). Texas Materials Inst.
An improved cathode material for a solid-oxide fuel cell would be a mixed electronic and oxide-ion conductor with a good catalytic activity for oxygen reduction at an operating temperature T{sub op} {le} 700 C and a thermal expansion matched to that of the electrolyte and interconnect. The authors report on the properties of Sr- and Ni-doped LaCoO{sub 3} and LaFeO{sub 3} perovskites that meet these criteria. Single-phase regions were determined by X-ray diffraction, and thermogravimetric analysis measurements were used to obtain the temperatures above which oxygen loss, and hence oxide-ion conductivity, occurs. The conductivity and Seebeck measurements indicate the coexistence of both p-type and n-type polaronic charge carriers resulting from an overlap of the Ni{sup III}/Ni{sup 2+} redox couple with the low-spin/intermediate-spin Co{sup IV}/Co{sup III} and high-spin Fe{sup 4+}/Fe{sup 3+} redox couples. Motional enthalpies {Delta}H{sub m} = 0.03, 0.02, and 0.08 eV, respectively, were estimated for Ni{sup 2+}, Co{sup IV}, and Fe{sup 4+} polarons. Optimal compositions have percolation pathways between dopants. Comparisons with transport data for the conventional cathode materials La{sub 1{minus}x}Sr{sub x}CoO{sub 3{minus}{delta}} and La{sub 1{minus}x}Sr{sub x}MnO{sub 3} indicate superior cathode performance can be expected.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 659127
- Journal Information:
- Journal of the Electrochemical Society, Vol. 145, Issue 9; Other Information: PBD: Sep 1998
- Country of Publication:
- United States
- Language:
- English
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