Abstract: Half-Heusler (HH) materials exhibit high thermoelectric performance, offering strong potential for efficient and reliable conversion of thermal-to-electrical energy. Comprehensive characterisation of the mechanical properties at operating temperatures is crucial for the practical application of such materials. Herein, the temperature-dependent tensile responses and failure mechanisms of p-type Zr_0.5Hf_0.5CoSb_0.8Sn_0.2 and n-type Zr_0.5Hf_0.5NiSn_0.985Sb_0.015 HHs were systematically investigated. High-temperature mechanical tests revealed that the tensile strength and elastic modulus of both HHs decreased with increasing temperature. The p-type HH retained its elastic load-bearing capacity throughout the tested temperature range (300-1100 K), whereas the tensile behaviour of the n-type HH transitioned from linear (at 300, 500, and 700 K) to nonlinear (at 900 and 1100 K). Micro-fractographic characterisation confirmed that oxidation and segregation intensified in both HHs at elevated temperatures, with the n-type HH exhibiting a greater reduction in grain boundary strength than the p-type HH. Temperature-dependent stress-strain relationships were established for both HHs to accurately describe their tensile responses. These findings provide valuable insights for designing reliable thermoelectric devices for engineering applications.

Key words: Tensile response, Failure mechanism, Half-Heusler materials, Temperature dependence