Thermoelectric performance of (GeTe)1-x(Sb2Te3)x fabricated by high pressure sintering method

(GeTe)(1-x)(Sb2Te3)(x) is one of good middle temperature thermoelectric materials. Here, the effects of x values and heat treatment (673 K24 h) on the thermoelectric property of (GeTe)(1-x)(Sb2Te3)(x) (x = 0, 0.02, 0.04, 0.06) prepared by solid-state synthesis (873 K) and high pressure sintering (6 GPa) method were studied, the composition, microstructure, and the thermoelectric properties in temperature range of 300-731 K were investigated. The results indicate that high pressure sintering (HPS) is beneficial to the dissolution of Sb2Te3 in GeTe and the acquisition of nanocrystalline (GeTe)(1-x)(Sb2Te3)(x). Soluble Sb2Te3 can greatly change the crystal structure of GeTe, and results in the high pressure phase and different thermoelectric property in (GeTe)(1-x)(Sb2Te3)(x) (x not equal 0). Heat treatment does not change the high pressure phase of (GeTe)(1-x)(Sb2Te3)(x) (x not equal 0), meanwhile it increases the crystal grain size of (GeTe)(1-x)(Sb2Te3)(x) (x not equal 0). Samples of x = 0.04 and x = 0.06 show the maximum Seebeck coefficient value at 724 K, and (GeTe)(0.98)(Sb2Te3)(0.02) shows the highest power factor (PF = 3.70 mu W/mmK(2) at 724 K). The largest value of ZT = 0.56 at 724 K is obtained for (GeTe)(0.94)(Sb2Te3)(0.06).