Regulating Multiscale Defects to Enhance the Thermoelectric Performance of CaAgDyMnO Ceramics.

Achieving high thermoelectric properties of CaMnO ceramics is significant for its applications at high temperature. Herein, CaAgDyMnO ceramics with plate-like template seeds additives were prepared by using a solid-state reaction method. The multiscale defects, including grain boundaries, oxygen defects, and Ag nanoprecipitations, which were regulated by the different sintering atmospheres, were beneficial for electron transport and phonon scattering. The grain boundaries as coherent interfaces could act as an alternative phonon scattering source. Oxygen vacancies coupled with Ag nanoprecipitations were verified by geometric phase analysis and annular bright-field analysis. The decrement in oxygen vacancies concentration strongly depended on the enriched oxygen environment, which could reduce electrical resistivities. Compared to the sample sintered at Ar atmosphere, a 17.5 times increment in power factor and a 20.1% reduction of the total thermal conductivity were obtained for the sample sintered at O atmosphere. As a result, the maximum value of 0.22 was obtained at 500 °C. It is an effective way for improving the thermoelectric performance of oxide-based thermoelectric materials.