Double perovskite Pr2CoFeO6 thermoelectric oxide: Roles of Sr-doping and Micro/nanostructuring

Abstract

Owing to their excellent thermal stability, non-toxicity, and low cost, oxide-based thermoelectric materials have considerably expanded research interests and industrial application. Here, we, for the first time, report a new-type Pr2CoFeO6 oxide-based thermoelectric materials from both theoretical and experimental aspects. Our first-principles calculation results indicate that Pr2CoFeO6 is a p-type semiconductor with narrow bandgap. The experimental thermoelectric evaluation shows that pristine Pr2CoFeO6, synthesized by a combination of sol–gel method and conventional sintering, has a peak figure of merit, ZT of 0.015 at 773 K with a high positive Seebeck coefficient of 250 μV K−1 and very low thermal conductivity of 0.7 W m−1 K−1 at this temperature. Further Sr2+ doping on Pr-sites (Pr3+) enhances the carrier concentration from 4.03 × 1014 cm−3 to 5.22 × 1017 cm−3, contributing to an improved power factor up to 46 μW m−1 K−2. Besides, Sr-doping induces point defects in the matrix and further suppresses the thermal conductivity to 0.58 W m−1 K−1, leading to a promising ZT up to 0.05 at 673 K in Pr1.8Sr0.2CoFeO6, which is significantly improved by 233% compared to pristine Pr2CoFeO6. We also predict that a high ZT of > 0.2 can be achieved by the optimization of carrier density, band engineering, and energy filtering, which is comparable to many other oxide-based thermoelectric materials.