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

• High performance of p-type BiSbTe based bimodal structures are fabricated. • bulk fracture displayed a dense & inhomogeneous diversification of mixed. grains. • high scattering rate of carriers/phonons increases α values & reduced κ values. • The Z T max of 1.202, and Z T Avg of 1.14 are obtained for the composite. structures. In this work, we fabricated bimodal structured high performance p-type BiSbTe alloys by combining coarse and sub-micron scale water atomized powder, 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 (0.95 W/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, Z T of 1.2, and Z T Avg of 1.14 was achieved in the bimodal structure specimen, due to its high-power factor, and low thermal conductivity. [Display omitted] [ABSTRACT FROM AUTHOR]