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 Sn0.85-xSb0.15MgxTe (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 zTmax reaches ∼1.02 and the device zTdevice of ∼0.50 at 773 K for Sn0.79Sb0.15Mg0.06Te, suggesting this SnTe-based composition has a promising potential in intermediate temperature thermoelectric applications.

Synthesis and thermoelectric properties of Rashba semiconductor BiTeBr with intensive texture.

Bismuth tellurohalides with Rashba-type spin splitting exhibit unique Fermi surface topology and are developed as promising thermoelectric materials. However, BiTeBr, which belongs to this class of materials, is rarely investigated in terms of the thermoelectric transport properties. In the study, polycrystalline bulk BiTeBr with intensive texture was synthesized via spark plasma sintering (SPS). Additionally, its thermoelectric properties above room temperature were investigated along both the in-plane and out-plane directions, and they exhibit strong anisotropy. Low sound velocity along two directions is found and contributes to its low lattice thermal conductivity. Polycrystalline BiTeBr exhibits relatively good thermoelectric performance along the in-plane direction, with a maximum dimensionless figure of merit (ZT) of 0.35 at 560 K. Further enhancements of ZT are expected by utilizing systematic optimization strategies.

Anisotropic thermoelectric properties of layered compound SnSe2.

Similar to high performance SnSe thermoelectrics, SnSe2 is also a layered structured semiconductor. However, its anisotropic thermoelectric properties are less experimentally investigated. In this work, Cl-doped SnSe2 bulk materials are successfully prepared, and their thermal stability and anisotropic transport properties are systematically studied. Unexpectedly, different from the theoretical prediction and other typical layered thermoelectric compounds like Bi2Te3, the out-of-plane zTc value is higher than in-plane zTa for the same composition. The zT value is significantly enhanced by Cl doping. A maximum zTc of ∼0.4 at 673 K is achieved in SnSe1.88Cl0.12, twice higher than previously reported Cl-doped SnSe2 synthesized by the solvothermal method.