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

In this paper, a series of S0.05Co4Sb11.6Te0.4 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 alpha, electrical resistivity rho, and thermal conductivity kappa were measured between 295 K and 773 K. The minimum thermal conductivity of S0.05Co4Sb11.6Te0.4 synthesized at 3.0 GPa was 1.23 Wm-1 K-1, and its maximum zT value reached 1.07 at 773 K, especially the lattice thermal conductivity was as low as 0.49 Wm-1 K-1.