Synthesis Optimization and Thermoelectric Properties of S-Filled and Te-Se Double-Substituted Skutterudite under High Pressure.

Abstract

In recent years, skutterudite filled with electronegative elements (S, Se, Cl, Br) has attracted the extensive attention of researchers. By doping electron donors (Pb, Ni, or Te, S, Se) at the Co or Sb sites, the electronegative elements can form thermodynamically stable compounds in the intrinsic pores of the skutterudite, substantially expanding the research scope of skutterudite. In this study, S0.05Co4Sb11.3Te0.6Se0.1 skutterudite was synthesized at high pressure and high temperature, with a pressure range of 2.0-3.5 GPa. The phase composition, micro-morphology, and electrical and thermal transport properties were systematically characterized. The micromorphology analysis shows that the introduction of S element and substituting Te and Se at the Sb sites inhibit the grain growth in a suitable high-pressure environment. Substantial differences are observed in the directions of the lattice stripes in the samples, and rich grain boundaries and many lattice distortions and dislocation defects occur. The carrier concentration can be optimized by filling the voids of the skutterudite with a few S atoms, and the thermoelectric properties can be optimized by scattering phonons through resonance scattering and defect scattering. The samples synthesized at a pressure of 3.0 GPa and a temperature of 900 K have a maximum power factor of 23.85 × 10-4 W m-1 K-2 and a maximum zT value of 1.30 at a test temperature of 773 K.