Approaching the minimum lattice thermal conductivity of p-type SnTe thermoelectric materials by Sb and Mg alloying

SnTe, as the nontoxic analogue to high-performance PbTe thermoelectric material, has captured the worldwide interest recently. Many triumphant instances focus on the strategies of band convergence, resonant doping, and nano-precipitates phonon scattering. Herein, the p-type SnTe-based materials Sn_0.85-xSb_0.15Mg_xTe (x = 0-0.10) are fabricated and a combined effect of Sb and Mg is investigated. Sb alloying tunes the hole carrier concentration of SnTe and decreases the lattice thermal conductivity. Mg alloying leads to a nearly hundredfold rise of disorder parameter due to the large mass and strain fluctuations, and as a consequence the lattice thermal conductivity decreases further down to ∼0.64 W m^-1 K^-1 at 773 K, close to the theoretical minimum of the lattice thermal conductivity (∼0.50 W m^-1 K^-1) of SnTe. In conjunction with the enhancement of the Seebeck coefficient caused by band convergence due to Mg alloying, the maximum zT_max reaches ∼1.02 and the device zT_device of ∼0.50 at 773 K for Sn_0.79Sb_0.15Mg_0.06Te, suggesting this SnTe-based composition has a promising potential in intermediate temperature thermoelectric applications.