Hot pressing effect on (Bi_0·25Sb_0·75)₂Te₃ mechanical and thermoelectric properties

Abstract

(Bi_0·25Sb_0·75)₂Te₃ thermoelectric material is a well known p type of compound that has higher figure of merit than other stoichiometries. The crystal of this compound was prepared, pulverized in a particle size ratio of 64% with a mesh of 80 (200 μm²) and 36% with a mesh of 60 (250 μm²). The powder was sintered in a heat up to 350–500°C under pressure of 500 MPa (hot pressing). To find out the temperature effects on thermal conductivity of the sample it was systematically investigated in nano-scale intrinsic structures by systems of X-ray diffraction, scanning electron microscopy and, for only once successful attempt, atomic force microscopy. The acquired images ensured to show homogeneous structures for hot pressed samples. In terms of thermal conductivity and with regard to the figure of merit (Z), optimum sintering temperature hovers at around 500°C, which leads to a maximum Z value of around 1·53 K⁻¹.