High-performance SnTe-based thermoelectric materials driven by band convergence and lattice softening via CuSbS₂ alloying and Cd doping

AbstractSnTe, as a lead-free analog of thermoelectric material PbTe, has garnered extensive attention for medium-temperature thermoelectric applications, yet its thermoelectric performance is severely hindered by high intrinsic carrier concentration, narrow band gap, and large lattice thermal conductivity. Herein, we report a two-step optimization strategy for SnTe, combining CuSbS₂ alloying and Cd doping to synergistically modulate its electronic and phonon transport properties. Electrically, CuSbS₂ alloying facilitates band convergence, which contributes to an enhanced density-of-states effective mass. Thermally, alloying weakens chemical bonding and induces ferroelectric instability, strengthening acoustic-optical phonon coupling and intensifying phonon scattering, thereby effectively suppressing the lattice thermal conductivity. Subsequent Cd doping further tailors the band structure, optimizes carrier concentration, and introduces additional point defects to enhance phonon scattering. As a result, the Sn_0.81Te_0.9Cd_0.09(CuSbS₂)_0.1 sample achieves a peak ZT of 1.0 at 773 K. This work highlights the critical role of chemical bond softening and ferroelectric instability induction in suppressing lattice thermal conductivity of chalcogenides.