Influence of Reaction-Sintering and Calcination Conditions on Thermoelectric Properties of Sm-doped Calcium Manganate CaMnO 3
Résumé
A wide range of solid-state synthesis routes for calcium manganate is reported in the literature, but there is no systematic study about the influence of the solid-state synthesis conditions on thermoelectric properties. Therefore, this study examined the influence of calcination temperature and calcination cycles on the Seebeck coefficient, electrical conductivity, and thermal conductivity. Higher calcination temperatures and repeated calcination cycles minimized the driving force for sintering of the synthesized powder, leading to smaller shrinkage and lower densities of the sin-tered specimens. As the electrical conductivity increased monotonously with increasing density, a higher energy input during calcination caused deterioration of electrical conductivity. Phase composition and Seebeck coefficient of sin-tered calcium manganate were not influenced by the calcination procedure. The highest thermoelectric properties with the highest power factors and figures of merit were obtained by means of reaction-sintering of uncalcined powder .