Mn alloying in SnTe increases the band gap and decreases the energy separation between the light and heavy hole valence bands, leading to a significant enhancement in the Seebeck coefficient. The maximum ZT of ~1.25 is found at 920 K for p-type SnMn_0.07Te.

SnCd_xTe materials were synthesized by the zone-melting method for this thermoelectric performance study. The X-ray diffraction results show that the lattice parameter decreases with increasing x, following Vegard's law of rock-salt structure SnTe and CdTe. Besides, the room temperature Seebeck coefficients of the SnCd_xTe system are enhanced to >60 μV K⁻¹, larger than those of Cd-doped SnTe synthesized by spark plasma sintering. A large power factor of ∼25 μW cm⁻¹ K⁻¹ is achieved in SnCd_0.12Te at 820 K, which rivals those of high performance PbTe-based materials. As a result, the highest ZT of ∼1.03 at 820 K was achieved for SnCd_0.12Te.

Tin selenite (SnSe) has attracted significant attention due to its record thermoelectric figure of merit (ZT=2.6 at 923 K) of its single crystal. However, the polycrystalline SnSe processes considerably less ZTs (⩽1.1). In this study, we investigate the thermoelectric properties of Ag-doped polycrystalline SnSe, which was synthesized via zone melting and hot pressing. By comparing our results and previous reports of Ag-doped single crystals and polycrystals, we determine that the high texturing degree is essential for achieving good thermoelectric performance in polycrystalline SnSe. The zone-melted Sn_0.99Ag_0.02Se shows better thermoelectric performance than the Ag-doped SnSe single crystal in the entire temperature range, exhibiting a peak ZT of 1.3 at 793 K.

SnTe has been known as a unique thermoelectric material to achieve the synergy of a resonant level and band convergence, originating from its characteristic band structure. In this work, we report an optimization of the two kinds of band engineering in In–Cd codoped SnTe. Owing to the complementary and competitive effects of the resonant level and band convergence, the location of the Fermi level is critical to the optimization. We show that the highest power factor and thermoelectric figure of merit ZT are reached by introducing Sn vacancies, rather than reducing Sn vacancies as normally done in SnTe. The peak ZT ∼ 1.1 appears at 850 K, while an overall enhanced ZT_ave of 0.54 between 300 and 850 K and an estimated conversion efficiency of 9% are obtained. This study discloses the non-trivial interplay between the resonant level and band convergence.

(Bi,Sb) ₂ Te ₃ composites with structure modifications by Ge _0.5 Mn _0.5 Te additions can simultaneously improve thermoelectric performance and mechanical properties.

A series of PbBr₂-doped polycrystalline SnSe samples were synthesized by melting and hot pressing. By PbBr₂ doping, the carrier concentration of SnSe was increased to 1.86 × 10¹⁹ cm⁻³ from 2.41 × 10¹⁷ cm⁻³, resulting in an increased electrical conductivity of 40 ± 2 S cm⁻¹ at 713 K while the undoped SnSe was only 5.1 ± 0.3 S cm⁻¹. Meanwhile, the PbBr₂-doped samples also exhibit a larger density of state effective mass (0.812m₀). Therefore, a high power factor of 4.8 ± 0.5 μW cm⁻¹ K⁻² and a peak ZT of 0.54 ± 0.1 were achieved at 793 K perpendicular to the hot pressing direction.