Texturing of (Bi0.2Sb0.8)2Te3 Nanopowders by Open Die Pressing

Open die pressing (ODP) at 370°C to 420°C has been employed as a straightforward forming process for sintering and texturing p-type (Bi_0.2Sb_0.8)₂Te₃ nanopowders. x-Ray diffraction pattern analysis 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 the orientation factor, f, by the Lotgering method, increased with decreasing final thickness of the samples. It was about f = 45% for 10-mm-thick samples and reached 70% for 2-mm-thick samples. Thermoelectric properties of ODP specimens were measured by the Harman method in the range from 20°C to 170°C. The dimensionless figure of merit, ZT, for 10-mm-thick samples was around 1 from room temperature up to 100°C.