Microcrystalline Bi_0.5Sb_1.5Te₃-Based Materials Prepared by Various Methods

Abstract—

We have studied properties of p-type Bi_0.5Sb_1.5Te₃ solid solution samples produced by hot pressing, extrusion, and spark plasma sintering of powders prepared by melt spinning and grinding the ingot in a jet mill to a particle size on the order of hundreds of microns or less than hundreds of nanometers (by mechanical activation). The powders and fracture surfaces of the samples have been examined on an optical and a scanning electron microscope. The powders prepared by melt spinning at disk rotation rates of 3000 and 5500 rpm had the form of platelets tens of microns in thickness, consisting of distinct regions ranging in thickness from a few to hundreds of nanometers. Microstructural analysis showed that all of the samples contained a small amount of tellurium, which was confirmed by X-ray microanalysis data. We have measured the thermoelectric parameters (Seebeck coefficient, electrical conductivity, and thermal conductivity) of the materials at room temperature and in the range 100–700 K and calculated their lattice thermal conductivity and thermoelectric figure of merit, ZT. The highest thermoelectric figure of merit, ZT = 1.0 ± 0.1 at 380 K, has been reached in the samples produced by spark plasma sintering and hot pressing of powders prepared by melt spinning and mechanical activation, respectively.