We prepared iodine-doped n-type SnSe polycrystalline by melting and hot pressing. The prepared material is anisotropic with a peak ZT of ~0.8 at about 773 K measured along the hot pressing direction. This is the first report on TE properties of n-type Sn chalcogenide alloys.With increasing content of iodine, the carrier concentration changed from 2.3×10 17 cm -3 (p-type)to 5.0×10 15 cm -3 (n-type) then to 2.0×10 17 cm -3 (n-type). The decent ZT is mainly attributed to the intrinsically low thermal conductivity due to the high anharmonicity of the chemical bonds like those in p-type SnSe. By alloying with 10 atm. % SnS, even lower thermal conductivity and an enhanced Seebeck coefficient were achieved, leading to an increased ZT of ~1.0 at about 773 K measured also along the hot pressing direction.

Na doping improved both the peak and average ZT of p-type polycrystalline SnSe.

In order to fabricate durable and efficient thermoelectric generators (TEG) for applications like automobile waste heat recovery, where thermal stress is a major concern, one needs to assess the mechanical performance of the TE materials. This work reports the hardness and elastic modulus of the moderate temperature range (200-1000 8C) TE materials, including halfHeusler, skutterudites, bismuth telluride, silicon germanium alloys, and lead selenide, using nanoindentation and atomic force microscopy (AFM). The p-type half-Heusler exhibits considerably higher hardness and modulus values, and lower brittleness as compared with other materials, which may be indicative of its more robust mechanical performance.

Ti, V, Cr, Nb, and Mo were found to be effective in increasing the Seebeck coefficient and power factor of n-type PbSe at temperature below 600 K. We found that the higher Seebeck coefficients and power factors are due to higher Hall mobility ~1000 cm 2 V -1 s

Good thermoelectric materials should have high engineering figure-of-merit (ZT) eng , not peak ZT, to achieve high conversion efficiency. In this work, we achieved a good (ZT) eng by optimizing the carrier concentration to improve the room temperature ZT using deep lying dopant, indium, in PbTe 1-y S y. It was found that a room temperature ZT as high as ~0.5 and a peak ZT ~1.1 at about 673 K were obtained in Pb 0.98 In 0.02 Te 0.8 S 0.2 due to a lower thermal conductivity by alloy scattering and Spinodal decomposition. The calculated efficiency could be as high as ~12% at cold side 323 K and hot side 773 K. The approach is expected to work in other materials systems too.