Thermoelectric and mechanical properties of Zn ₄Sb ₃ polycrystals sintered by spark plasma sintering

β-Zn ₄Sb ₃ has attracted much interest as a thermoelectric material because of its potential for power-generation applications in a moderate temperature range (450 ~ 650 K). In general, three kinds of considerations have been reported for the fabrication of a polycrystalline β-Zn ₄Sb ₃ bulk sample: (i) a problem in chemical stability, (ii) cracks in bulk specimens owing to a phase transition of the Zn ₄Sb ₃ composition resulting in stress during cooling, and (iii) the requirement for high bulk density. In this study, a pure Zn ₄Sb ₃ phase with a high define ZT(figure of merit) value was synthesized by using a vacuum melting process and a vacuum annealing process, followed by a spark plasma sintering (SPS) method. Fabricating a single-phase specimen with high bulk density by means of optimizing the SPS conditions (temperature and pressure) was significant for obtaining high performance in the Zn ₄Sb ₃ thermoelectric system. The maximum ZT value (0.98) was attained at a 573 K measurement temperature for the specimen sintered with the optimized SPS conditions (723 K, 40 MPa).