Combined hot extrusion and spark plasma sintering method for producing highly textured thermoelectric Bi2Te3 alloys

Hot extrusion is a promising method for producing high-performance thermoelectric bismuth telluride alloys because of its ability to create textured microstructures. However, hot extrusion is less favourable for scaling-up because of temperature and strain gradients along the radial direction, and only < 110 > -textured thermoelectric legs can be obtained because of the fibre-like texture. We suggest a way to overcome these disadvantages by implementing an additional spark plasma sintering process on a stack of extrudates. Using this combined process, we demonstrate the fabrication of 12 x 15 x 13 mm(3) p-type (Bi0.2Sb0.8)(2)Te-3 samples from extrudates that had originally been 3 mm in diameter. The evolution of sheet-like texture revealed by SEM, XRD, and EBSD allows us to obtain both < 110 > - and < 001 > -textured thermoelectric legs from a single specimen that are desirable for low- and high-temperature applications, respectively. Our results demonstrate the combined method as an industry-friendly process for fabricating high-performance thermoelectric materials.