Microwave sintering of CaMnO3 thermoelectric perovskites synthesized by modified Pechini method

[Display omitted] •Longer soaking times promoted sintering stage transition linked to grain growth.•Greater sintering soaking times favors microwave effect in CaMnO3 grain morphology.•Orthorhombicity and porosity influenced on polaron hopping conduction mechanisms.•Thermoelectric properties optimization promoted the highest efficiency. CaMnO3 perovskites are promising n-type metallic oxides for thermoelectric materials due to their high Seebeck coefficient, moderate electrical conductivity, and low thermal conductivity. The study analyzes samples obtained from powders synthesized by modified Pechini method and sintered by microwave irradiation at different temperatures and soaking times. In the sintered samples, CaMnO3 was the unique crystalline phase formed. Structural orthorhombicity decreased with increasing sintering soaking times. For ceramics sintered at 1573 K, the grain sizes were 0.46 µm, 1.98 µm and 3.03 μm for ceramics sintered without soaking time, for 15 min and for 30 min, respectively. The highest electrical conductivity values were obtained from CaMnO3 ceramic sintered at 1573 K for 15 min. The CaMnO3 perovskite sintered at 1573 K without soaking time exhibited the lowest thermal conductivity and the highest ZT and η values of about 0.016 and 0.48 %, respectively, making it the most promising for thermoelectric applications.