Microstructure and thermoelectric properties of porous CaMnO3 / CaMn2O4 composite prepared by spray solution combustion synthesis

Oxides are attractive and promising compounds for application as thermoelectric materials owing to thermal and chemical stability, cost-effectiveness, and environmental safety. In this work, CaMnO3 perovskite hollow spheres were synthesized by spray solution combustion synthesis. The effect of the fuel glycine on the phase composition, morphology, and microstructure of CaMnO3 was studied, and the influence of synthesis parameters on the characteristics of the bulk materials was investigated. The porous CaMnO3 (porosity 10 – 20%) forms by pressureless sintering at 1473K, which is accompanied by the precipitation of marokite CaMn2O4. It is possible to alter the porosity level as well as marokite and pore size in the CaMnO3 / CaMn2O4 composite by tailoring the fuel amount, which, in turn, affects the thermoelectric properties. The zT value of 0.13 at 1073K, to the best of our knowledge, is the highest zT reported for the undopted CaMnO3 material.