Synthesis and properties of mixed lanthanide chromite perovskites

Calcium-substituted lanthanum chromites were synthesized using a mixed lanthanide precursor composed primarily of La, Nd, Cc, and Pr The thermal and electrical properties of these materials were measured and compared to similar chromites synthesized with lanthanum nitrate. The presence of Nd and Pr in the chromite resulted in a lowering of the thermal expansion coefficient and an increase in the temperature necessary to attain full density. Arrhenius plots of electrical conductivity were nonlinear with an inflection at temperatures between 625 and 750 degrees C, indicating an increase in the carrier concentration with temperature. The increase in carrier concentration was consistent;with the reduction of Ce4+ to Ce3+, resulting in a corresponding increase in Cr4+ in order to preserve electrical neutrality. The presence of both tri- and tetravalent Cc was substantiated using dilatometry measurements and X-ray photoelectron spectroscopy. The mixed lanthanide precursor is a possible low cost alternative for the synthesis of rare earth chromites for applications such as interconnects in solid oxide fuel cells.