Abstract
Sb2Te3 bulks with various porosities are synthesized via applying different pressures and processes. Pores defect variations are demonstrated by positron annihilation spectroscopy measurement. Through tuning sintering temperature and pressure exerted in one step or two steps, pores and interfaces of the materials are tailored, which enhances the Seebeck coefficient, simultaneously maintains high electrical conductivity and remarkably reduces thermal conductivity. A maximum ZT of 1.17 is obtained at 523 K for Sb2Te3 samples compacted in two steps under 10 kN, increasing by 54.1% as compared to corresponding sample under 1 kN. Lattice thermal conductivity calculation by modified BET model combining with effective medium theory fits with experiments data, revealing porosity manipulation plays a significant role in reducing thermal conductivity.