Vacancy engineering in rock-salt type (IV-VI)_x(V-VI) materials for high thermoelectric performance

This study proposes a rational approach for controlling vacancy and carrier concentrations simultaneously by introducing V-VI chalcogenide into rock-salt structured IV-VI, where V, IV, and vacancy occupy the cationic sites, and VI occupies the anionic sites. For proof-of-concept experiments, Sb₂Te₃ is introduced in SnTe matrix, leading to the formation of vacancies (□Sn_xSb₂Te_x+3, where □ is vacancy) and dense dislocations in grains, along with an optimization of p-type carrier concentrations. Unlike simple Sb-doped Sn_1-xSb_xTe samples, the □Sn_xSb₂Te_x+3 samples in this study show a much lower lattice thermal conductivity and an enhanced power factor at a similar carrier concentration level. Specifically, the lattice thermal conductivity of □Sn₁₀Sb₂Te₁₃ sample approaches the theoretical value of SnTe (amorphous limit) due to the strong phonon scattering caused by the large difference in mass and local strain near the dense dislocations formed from the clustering of vacancies and partly from the scattering from Sb. Such simple approach leads to boosting the thermoelectric performance of SnTe without any complex manipulations by using high-cost, harmful dopants.