Modelling oxidation kinetics of half-Heusler thermoelectric materials and the role of protective coatings

Abstract Thermoelectric (TE) materials are increasingly utilised for electricity generation by harvesting waste heat in various practical applications. When deployed in high-temperature environments, their long-term thermal stability is crucial for ensuring high reliability and minimised mechanical degradation. While state-of-the-art experimental studies have highlighted the potential of half-Heusler TE materials in energy harvesting, experimental testing durations are often limited, leaving long-term performance uncertain. This paper addresses these gaps through finite element-based oxidation modelling, which explicitly accounts for the influence of protective coatings. Oxygen diffusion is modelled with a 1D Fick’s equation solved with FEniCSx, with a time-decaying diffusivity in both the substrate and coating domains. The model is calibrated against 50 h mass-gain data for uncoated and CrSi-coated half-Heusler TE materials. With the calibrated parameters, the framework is used to extrapolate mass gain and oxide-scale growth, and can serve as a tool for estimating the long-term thermal stability of TE materials protected by oxidation-resistant coatings.