Texturing of (Bi0.2Sb0.8)2Te3 nanopowders by open die pressing

Open Die Pressing (ODP) at 370 ÷ 420 °C has been employed as a straightforward forming process for sintering and texturing p-type (Bi0.2Sb0.8)2Te3 nanopowders. X-ray diffraction pattern showed that ODP samples were strongly textured, with the basal (00l) planes of the hexagonal crystal cell oriented parallel to the pressing plates. The degree of texturing, evaluated as orientation factor, f, by the Lotgering method, increased by decreasing the final thickness of the samples. It was about f = 45% for 10 mm thick samples and reached 70% for 2 mm thick ones. Thermoelectric properties of ODP specimens were measured by Harman method in the range of 20 to 170 °C. The dimensionless figure of merit, ZT, for 10 mm thick samples was around 1 from room temperature up to 100 °C.