Materials Science

Cooler Running

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Science  17 Feb 2006:
Vol. 311, Issue 5763, pp. 921
DOI: 10.1126/science.311.5763.921c

Current solid-oxide fuel cells run at 500° to 700°C. Lower temperature operation is desirable but must overcome low electronic and ionic conductivity in the ceramic cathode materials [typically (La,Sr)MnO3 or (La,Sr)(Fe,Co)O3] where oxygen is adsorbed and reduced to oxide. Kim et al. have found that the oxygen-deficient double-perovskite material PrBaCo2O5+δ (PBCO) has high electrical conductivity (∼100 Siemens per square centimeter) and rapid oxygen transport kinetics at 300° to 500°C. Prior screening for improved cathodes has generally assessed candidate materials in porous bulk morphologies. To achieve a more precisely ordered microstructure, the authors prepared the PBCO as an epitaxial thin film, which was grown on strontium titanate by pulsed laser deposition. They speculate that the increase in oxygen surface exchange rate relative to that of disordered perovskites may arise from the alignment of the PBCO c axis in the film plane, which raises the concentration of vacancies into which oxide can diffuse. — PDS

Appl. Phys. Lett. 88, 024103 (2006).

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