The influence of high pressure induced lattice dislocations and distortions on the thermoelectric performance of pristine SnTe

As a sister compound of PbTe, SnTe possesses the environmentally friendly elements. However, the pristine SnTe compounds suffer from the high carrier concentration, the large valence band offset between the L and Σ positions and high thermal conductivity. Using high-pressure and high-temperature technology, we synthesized the pristine SnTe samples at different pressures and systemically investigated their thermoelectric properties. High pressure induces rich microstructures, including the high-density dislocations and lattice distortions, which serve as the strong phonon scattering centers, thereby reducing the lattice thermal conductivity. For the electrical properties, pressure reduces the harmful high carrier concentration, due to the depression of Sn vacancies. Moreover, pressure induces the valence band convergence, reducing the energy separation between the L and Σ positions. The band convergence and suppressed carrier concentration increase the Seebeck coefficient. Thus, the power factors of pressure-sintered compounds do not deteriorate significantly under the condition of decreasing electrical conductivity. Ultimately, for a pristine SnTe compound synthesized at 5 GPa, a higher ZT value of 0.51 is achieved at 750 K, representing a 140% improvement compared to the value of 0.21 obtained using SPS. Therefore, the high-pressure and high-temperature technology is demonstrated as an effectively approach to optimize thermoelectric performance.