Enhanced thermoelectric performance in Ca-substituted Sr3SnO

First-principles calculations were performed to study the electronic and thermoelectric transport properties of Ca-substituted Sr3SnO (Sr(3-x)Cas(x)SnO, 3 >= x >= 0). The effects of Ca substitution on the bandgap are studied, and detailed mechanisms are proposed to explain the results obtained. We found that an increase of the hole concentration reduces the effective mass and the Seebeck coefficient of Ca-substituted Sr3SnO. The optimum hole concentration was obtained for Sr2CaSnO, and the corresponding maximum Seebeck coefficient of 219 mu V/K was obtained at 500 K. The electrical conductivity of Sr3SnO and its alloys has a semiconducting nature, which contradicts experimental results for Ca3SnO. We found that Ca-deficient Ca3SnO exhibits metallic conductivity, and this removes the contradiction with our results. The lattice thermal conductivities (k(1)) of Sr3SnO and Ca3SnO were calculated by use of both the Perdew-Burke-Emzerhof functional and the GW functional. The total thermal conductivity for Sr3SnO and Ca3SnO at 300 K is 3.03 and 2.06 W/(m K), respectively. The figure of merit (ZT) for Sr2CaSnO at 500 K is 0.6, making it promising for thermoelectric applications.