Preparation and Thermoelectric Transport of Polycrystalline In sub(4)Se sub(3) with High Figures of Merit

Polycrystalline In sub(4)Se sub(3) thermoelectric materials were synthesized in the processing sequence of vacuum melting, annealing and spark plasma sintering. The effect(s) of melting and annealing duration periods on the phase, composition, microstructure, and thermoelectric properties of polycrystalline In sub(4)Se sub(3) were investigated. After the melting process, both In and InSe phase were detected in the ingots. With increasing melting duration time, an increase in Se deficiency was observed, leading to an increase of carrier concentration, which contributed to the observed improvement of electrical conductivity. The specimen melted for 48 h showed relatively higher ZT. Thus on the basis of 48 h melting process, the ingots were then annealed for different periods of time, which eliminated the presence of InSe phase. After annealing, scattered large step-like structures were observed in the matrix, which favored the reduction of thermal conductivity but had no significant influence on the electrical