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 ∑ positions and high thermal conductivity. Using high pressure and high temperature technology, we have synthesized the pristine SnTe samples at different pressure and systemically investigated their thermoelectric properties. High pressure introduced rich microstructures, including the high density dislocations and lattice distortions, which served as the strong phonon scattering centers, thereby reducing the lattice thermal conductivity. For the electrical properties, pressure reduced the harmful high carrier concentration, due to the depression of Sn vacancies. Moreover, pressure induced the valence band convergence, reducing the energy separation between the L and ∑ positions. The band convergence and suppressed carrier concentration increased the Seebeck coefficient. Thus, the power factors of pressure-sintered compounds did not deteriorate significantly under the condition of electrical conductivity decreases. Ultimately, for a pristine SnTe compound synthesized at 5 GPa, a higher ZT value of 0.51 was achieved at 750 K, representing an 140% improvement compared to the value of 0.21 obtained using SPS. Therefore, the high-pressure and high-temperature technology has been demonstrated as an effectively approach to optimize thermoelectric performance.