Electrical transport properties of Ca0.9La0.1−xBixMnO3−δ (0 ≤ x ≤ 0.1) thermoelectric materials

A series of Ca0.9La0.1−xBixMnO3−δ (0 ≤ x ≤ 0.1) was fabricated by cold compaction and tape casting methods. The microstructural and thermoelectric properties of Ca0.9La0.1−xBixMnO3−δ were studied, with respect to the partial substitution of Bi3+ for La3+. All of the sintered Ca0.9La0.1−xBixMnO3−δ crystallized in the orthorhombic perovskite structure, belonging to the Pnma space group. The substituted Bi3+ significantly increased grain size and density because it acted as a sintering additive. The electrical conductivities of tape casting-processed Ca0.9La0.1−xBixMnO3−δ were much higher than those of cold compaction-processed Ca0.9La0.1−xBixMnO3−δ. On the other hand, the absolute values of the Seebeck coefficient for tape casting-processed Ca0.9La0.1−xBixMnO3−δ were similar to those of cold compaction-processed Ca0.9La0.1−xBixMnO3−δ. Consequently, tape casting-processed Ca0.9La0.1−xBixMnO3−δ showed a much higher power factor in comparison with cold compaction-processed Ca0.9La0.1−xBixMnO3−δ. The partial substitution of La3+ by Bi3+ up to x = 0.05 led to an increase in the power factor. The highest power factor (3.01 × 10−4 Wm−1·K−2) was obtained for tape casting-processed Ca0.9La0.05Bi0.05MnO3−δ at 800 °C.