Melt-spun Sn1−−Sb Mn Te with unique multiscale microstructures approaching exceptional average thermoelectric zT

Abstract

SnTe has attracted worldwide attention as a non-toxic candidate material for thermoelectric applications; however, un-modified SnTe possesses inferior thermoelectric properties. Herein, we report the significantly improved thermoelectric performance in Sb, Mn-codoped SnTe synthesized by energy-efficient melt spinning. Sb segregation was observed at the grain boundaries of Sb-doped and Sb, Mn-codoped SnTe melt-spun ribbons, leading to grain refinement; subsequent sintering promotes the diffusion of Sb while retains Sb-rich particles. Initially, intensified phonon scattering from unique multiscale microstructures, including point defects, Sb-rich particles and high-density dislocations generated after Sb doping, effectively diminishes the lattice thermal conductivity of SnTe, leading to a substantially low value of 0.55 W m −1 K −1 in Sn 0.84 Sb 0.16 Te at 300 K. Further, the power factors are significantly enhanced via Mn doping owing to valence band convergence, verified by first-principles calculation. Consequently, a peak zT of ~ 1.27 at 773 K and an exceptional average zT of ~ 0.89 over 300–873 K are obtained in Sn 0.72 Sb 0.16 Mn 0.12 Te, which are ~ 110% and ~ 340% higher than those of SnTe, respectively. This study provides an effective pathway to synergistically improve the thermoelectric performance of SnTe by microstructure and band structure engineering, and establishes melt spinning as a controllable synthetic method to high-performance thermoelectrics. Sb and Mn co-doped SnTe materials, synthesized by combining fast melt spinning and hot pressing, achieve synergistically diminished lattice thermal conductivity and improved power factor, due to enhanced phonon scattering from unique multiscale microstructures and band convergence, respectively. Notably, the Sn 0.72 Sb 0.16 Mn 0.12 Te sample delivers an excellent average zT of ~ 0.89 in the temperature range of 300–873 K. • Synthesizing Sb and Mn codoped SnTe by energy-efficient melt spinning. • Clarifying the vital role of Sb doping in grain refinement of melt-spun SnTe. • Diminishing the lattice thermal conductivity by multiscale microstructures. • Optimizing thermoelectric properties by structure and band engineering. • Obtaining an exceptional average zT of 0.89 (300–873 K) in Sn 0.72 Sb 0.16 Mn 0.12 Te.