Influence of B site substituents on lanthanum calcium chromite nanocrystalline materials for a solid-oxide fuel cell

Abstract

Highly reactive and nanocrystalline powders of LaCrO(3)based compositions, having the general formula La0.9Ca0.1Cr1-xMxO3-delta (0 <= x <= 0.1, and M=Al, Co, or Mg), suitable for solid-oxide fuel cell (SOFC) applications, have been synthesized using an auto-combustion technique with ammonium dichromate as the chromium source. Owing to very fine crystallite size (ranging from 10 to 50 nm) and the high reactivity of the powders (surface area as high as 25 m(2)/g), the sintering temperature reduces drastically and a highly dense, uniform, and fine-grained microstructure is obtained. A dramatic improvement in densification (nearly theoretical density) is observed for aluminum substitution, when sintered at as low a temperature as 1300 degrees C. The microstructure shows a uniform distribution of grains having an average grain size of similar to 0.5 mu m. Depending on the substituent, the electrical conductivities of the sintered samples in air, at 1000 degrees C, were found to be in the range of 10-45 S/cm, and are more than that of the values required for SOFC application. The thermal expansion coefficients, as obtained, are also comparable with the other SOFC cell components

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