High Thermoelectric Performance of SnTe–MnSe with Low Lattice Thermal Conductivity

SnTe, a nontoxic thermoelectric (TE) material, has attracted considerable attention due to its lead-free rock-salt, which is comparable to PbTe. In this study, an alloying strategy is used to embed MnSe in the SnTe matrix, which results in synergistic effects of valence-band convergence and defect engineering. The MnSe-alloyed SnTe achieves an excellent thermoelectric performance. Mn- and Se-substitutions of Sn and Te sites, respectively, induce the convergence of valence bands and increase the Seebeck coefficients of samples, which lead to competitive power factors. In addition, the numerous defects introduced by alloying with MnSe act as phonon scattering sources to effectively lower the lattice thermal conductivity. The SnTe–10%MnSe sample exhibited a lattice thermal conductivity of 0.44 W m–1 K–1 at 823 K. Ultimately, the SnTe–8%MnSe sample achieved a figure of merit of 1.02, which was 276% higher than that of undoped SnTe. This study offers an approach to enhancing Te-based thermoelectric materials with low lattice thermal conductivity and to advancing the fundamental understanding of SnTe.