Structural Stability and Thermoelectric Properties of CoSbS under High Pressure.

The structural stability of CoSbS under extremely high-pressure conditions was investigated by using in situ high-pressure X-ray diffraction. Remarkably, CoSbS demonstrates exceptional structural stability even at ∼60 GPa. Building upon these stable structural characteristics, we employed first-principles calculations and Boltzmann transport theory to analyze the electronic structure and thermoelectric properties of CoSbS under high pressure. The study reveals that pressure significantly modifies the electronic structure of CoSbS, leading to a progressive reduction in the band gap, pronounced energy band convergence near the conduction band minimum, and a substantial decrease in carrier effective mass. Simultaneously, the synergistic interaction between heavy and light bands under high pressure induces concurrent enhancement of electrical conductivity and preservation of the high Seebeck coefficient. This cooperative effect yields an exceptional power factor of 88 μW cm-1 K-2. Unfortunately, under high pressure, the reduction in phase space and Grüneisen parameter during three-phonon scattering, combined with increased phonon specific heat and relaxation time, diminishes the anharmonic scattering effect of phonons in CoSbS, leading to an increase in the lattice thermal conductivity. The results demonstrated that high-pressure regulation could optimize the electrical transport properties of materials, offering valuable insights for exploring other thermoelectric materials and elucidating the influence of high pressure on the thermal transport properties.