Low lattice thermal conductivity by alloying SnTe with AgSbTe2 and CaTe/MnTe

SnTe-AgSbTe2 alloys have shown promising thermoelectric performance due to phonon-vacancy scattering, while SnTe alloyed with high-solubility monotellurides such as CaTe/MnTe has also shown enhanced thermoelectric performance owing to band convergence. However, to what level the combined effect on thermoelectrics by alloying SnTe with AgSbTe2 and CaTe/MnTe exists, especially for the quantitative relationship between the vacancy concentration and lattice thermal conductivity, still remains a mystery. Here, a spontaneous strategy has shown that combining AgSbTe2 with CaTe/MnTe in SnTe alloys can lead to an inherent valence band convergence and improved electronic performance. In particular, a low lattice thermal conductivity (similar to 0.4W/m K), which approaches the amorphous limit of SnTe, is achieved in (Sn0.95Ca0.05Te)(0.75)(AgSbTe2)(0.125) with 3% excess of Sn. The Debye-Callaway model provides a good clarification of underlying physics for the reduced lattice thermal conductivity as well as quantifies the contribution of vacancy scattering. The present finding demonstrates the excellent potential for advancing the thermoelectric performance by SnTe-based alloys.