Enhanced power factor in CaMnO3-based thermoelectric ceramics via co-doping

• Nb-doped CaMnO 3 were synthesized via planetary milling and sintered at 1583 K for 12 h. • XRD analysis confirmed the presence of the desired thermoelectric phase, with minimal CaMn 2 O 4 secondary phase detected. • SEM showed Nb reduced grain size and resistivity, reaching 9.2 mΩ cm at 1073 K in 0.03 Nb-doped samples. • A peak power factor of 0.48 mW/K 2 m at 1073 K was achieved in 0.01 Nb-doped samples. • Estimated ZT values highlight the potential of Nb-doped CaMnO 3 for thermoelectric applications. Nb-doped Ca 0.97 Y 0.01 La 0.01 Yb 0.01 Mn 1-x Nb x O 3 materials were prepared to assess their thermoelectric properties. Samples were obtained by sintering at 1583 K for 12 h involving planetary milled precursors. XRD analysis indicated primarily thermoelectric phase with minor CaMn 2 O 4 . Microstructural observations revealed decreasing grain size with increasing Nb content. However, electrical resistivity decreases for the samples with Nb-content up to 0.03, which can be associated with the increase of the charge carrier concentration. The lowest value at 1073 K (9.2mΩcm) is among the best reported in the literature. Seebeck coefficient decreased with Nb-doping, and the best PF value at 1073 K has been determined for 0.01Nb samples (∼0.48mW/K 2 m). Assuming the thermal conductivity at 1073 K similar to that at 473 K, the calculated ZT values are among the typically reported in this family. These results highlight the promise of CaMnO 3 -based materials for integration in thermoelectric modules working under steady-state mode, where the high PF values are of great importance.