Thermoelectric performance of BaBiNa and SrBiNa: A first-principle study

Abstract

The high thermoelectric performance is expected to develop practical thermoelectric materials. The relationship between the dimensionless figure of merit (ZT) and the carrier concentration and the temperature is constructed to identify the best thermoelectric performance of XBiNa (X = Ba and Sr). The electronic structure and transport properties of the two semiconductors are calculated by combining the first-principle DFT with the semi-classical Boltzmann transport theory to obtain the Seebeck coefficient, electronic thermal conductivity, and electrical conductivity. The relaxation time is determined by the deformation potential theory, and the lattice thermal conductivity is calculated by the Slack model. The maximum ZTs of 1.14 and 1.16 can be achieved for the n-type BaBiNa and SrBiNa at a carrier concentration of 5.62 × 1018/3.60 × 1018 cm−3 at 800 K, respectively. The maximum thermoelectric conversion efficiency of 21.25 % is attributed to the n-type SrBiNa, implying that the compound is potential thermoelectric material. The different thermoelectric mechanisms for the n- and p-type XBiNa are elucidated through evaluating the tendency of the transport coefficients and ZT.