Thermal transport and thermoelectric properties of alkali-metal telluride Na2Te from first-principles study

The excellent thermoelectric performance of alkali-metal telluride Na2Te has been systematically studied from the electronic and phonon transport properties within the density functional theory combined with the Boltzmann transport theory framework. The phonon dispersion without any imaginary mode demonstrates that the Na2Te compound is dynamically stable. The calculated lattice thermal conductivity is as small as 3.01 W m−1 K−1 at room temperature, suggesting that Na2Te can serve as a promising thermoelectric material. The related anharmonic effect parameters, phonon lifetime and Grüneisen parameter, are discussed to further explain the lattice thermal conductivity. Also, the electronic transport parameters, such as Seebeck coefficient S, electrical conductivity σ, and electronic thermal conductivity κe, are investigated to determine the thermoelectric performance by utilizing the semi-classical Boltzmann transport theory. The final figure of merit ZT can be evaluated based on the lattice thermal conductivity and the corresponding electronic transport coefficients. The maximum ZT of 1.53 can be achieved at a carrier concentration n = 3.08 × 1020 cm−3 for p-type Na2Te at T = 900 K, greatly larger than that of the n-type Na2Te (0.86), suggesting that the Na2Te can be a potential p-type thermoelectric material.