Realizing high thermoelectric properties through the development of bimodal microstructures using water atomized p-type Bi0.5Sb1.5Te3 alloys

In this work, we fabricated bimodal structured high performance p-type BiSbTe alloys by combining coarse and sub-micron scale water atomized powders, followed by spark plasma sintering. The bulk fracture analysis revealed a dense and inhomogeneous distribution of mixed grains on the surface, while the texture analysis using EBSD revealed that the bulk specimens had a bimodal microstructure with random grain alignment due to the distribution of initial powder sizes. The coarse grain specimen exhibited high electrical conductivity of 1257 Ω−1cm−1 because of its high carrier mobility and carrier concentration. A high Seebeck coefficient (214 μV/K) and low thermal conductivity (0.95W/mK) were observed for the bimodal structured specimens because scattering of carriers and phonons was higher compared with the coarse specimen. The maximum thermoelectric figure of merit, ZT of 1.2, and ZTAvg of 1.14 was achieved in the bimodal structure specimen, due to its high-power factor, and low thermal conductivity.