Comprehensive Study of ZrNiIn0.5Sb0.5 Double Half-Heusler Properties for Thermoelectric and Spintronics Applications: Intrinsic Homogeneity Optimization and Extrinsic Sc Doping Effects

Recent efforts have focused on optimizing alternative thermoelectric (TE) materials for mid-to-high temperature applications and exploring additional potential fields of application. This study aimed to improve the TE performance of ZrNiIn_0.5Sb_0.5 double half-Heusler alloy by reducing impurity phases and doping with Sc, while also probing its magnetic behavior. Samples were synthesized through arc melting, hot pressing, and annealing, which resulted in a reduction in impurities upon stepwise In–Sb compensation. This improvement led to a 114% increase in power factor (PF) and a 30% decrease in thermal conductivity. Furthermore, the retention of ZrO₂ nanoprecipitates and a bimodal microstructure, along with further minimization of impurities through Zr compensation, increased PF by an additional 20% and decreased thermal conductivity by 12%. As a result, the figure of merit (zT) was boosted by 82% at 973 K. However, Sc doping caused a reduction in thermal conductivity by 11%, but it had a negative impact on PF and thus zT. ZrNiIn_0.5Sb_0.5 demonstrated a hardness of 447 Hv and exhibited soft ferromagnetic semiconductor properties. This research significantly advances the use of ZrNiIn_0.5Sb_0.5 alloys for thermoelectric applications and potential spintronic applications.