S-filled and Te-doped CoSb3 materials prepared by HPHT method with ultra-low thermal conductivity

Abstract

In this paper, a series of S[Formula: see text]Co4Sb[Formula: see text]Te[Formula: see text] samples were prepared by high pressure and high temperature (HPHT) method under different pressures. The synthesis time was shortened from several days to 0.5 h. Te doping and S filling simultaneously optimized the thermal and electrical transport properties of the CoSb3 materials. We found a porous architecture containing rich grain boundaries, different grain sizes, nano- to micrometer-sized pores, and a large number of dislocations, which can scatter a wide spectrum of phonons. Seebeck coefficient [Formula: see text], electrical resistivity [Formula: see text], and thermal conductivity [Formula: see text] were measured between 295 K and 773 K. The minimum thermal conductivity of S[Formula: see text]Co4Sb[Formula: see text]Te[Formula: see text] synthesized at 3.0 GPa was 1.23 Wm[Formula: see text] K[Formula: see text], and its maximum zT value reached 1.07 at 773 K, especially the lattice thermal conductivity was as low as 0.49 Wm[Formula: see text] K[Formula: see text].