Impact of spark plasma sintering temperature on the structure and thermoelectric properties of the Ti0.5Zr0.5NiSn alloy

Spark plasma sintering (SPS) has been proven as an advanced densification technique in which the bulk materials can be retained with nano-scale grain structure during the sintering process at low temperatures and in a short time. However, most (Ti, Zr, Hf)NiSn-based alloys have been reported with synthetic procedures using high sintering temperatures above 1273 K. High sintering temperature could lead to changes in phase structure and promote grain growth, which may adversely affect the phonon and charge transport properties. In this work, based on Ti_0.5Zr_0.5NiSn alloy prepared by a short-time synthesis process using the arc melting combined melt spinning method, we investigated the effect of SPS temperature on the evolution of phase structure, morphology and the thermoelectric properties of this alloy. The results exhibited that SPS at different temperatures significantly changed the morphology and electrical properties of Ti_0.5Zr_0.5NiSn alloy. The total thermal conductivity was obtained with relatively low values varying between 2.73 and 3.4 Wm⁻¹K⁻¹. The dimensionless figure of merit ZT results reveal that higher sintering temperatures above 1073 K did not improve the ZT value. The highest ZT value of 0.81 at 817 K with an average ZT of 0.53 in the temperature range between 307 and 861 K was achieved for the optimized sintering temperature of 1073 K. Short synthetic time and at low sintering temperature for maintaining the thermoelectric performance of the Ti_0.5Zr_0.5NiSn alloy are important in terms of energy saving and the safety of the sintering system.