Enhancing thermoelectric performance of TiXPt (X = Ge, Sn) via nanostructuring

Half-Heusler compounds are promising candidates for medium- to high-temperature thermoelectric applications due to their thermal stability, mechanical robustness, and tunable electronic properties. Many 18-electron half-Heusler compounds have been extensively investigated for their thermoelectric properties; however, some remain unexplored. In this work, we use first-principles calculations and Boltzmann transport theory to investigate the transport properties of TiGePt and TiPtSn. Our results show that both materials have high power factors, but their efficiency is limited by their high intrinsic lattice thermal conductivity. To address this, we examine nanostructuring via grain-size reduction, a composition-preserving strategy, to enhance phonon scattering. Our results demonstrate that reducing the grain size suppresses lattice thermal conductivity with minimal impact on the power factor. This reduction outweighs any degradation in electronic transport, resulting in a net enhancement of the thermoelectric figure of merit, ZT.