TiO2-driven ZrO2 leads to the high thermoelectric performance of ZrNiSn half-Heusler alloy
Résumé
This work demonstrates a nanocomposite approach to reduce the thermal conductivity of the half-Heusler alloy ZrNiSn using TiO2 (0.0–2.5 wt. %) nanoparticles inclusion that induce the formation of ZrO2. The presence of ZrO2 promotes the formation of Zr vacancies resulting in-gap energy states and leading to a boost in electrical conductivity. A large reduction in the lattice thermal conductivity was observed in all the TiO2-dispersed ZrNiSn samples owing to enhanced phonon scattering from various defects including TiO2 nanoparticles, in-situ formed ZrO2 secondary phase, grain boundaries, edge dislocations, and vacancies interfaces. Thus, the dispersion of TiO2 in the ZrNiSn matrix results in the optimum electronic transport and reduced thermal conductivity, resulting in a peak ZT of ~ 0.73 at 775 K for 1.5 wt. % TiO2/ZrNiSn composite, which represents an improvement of ~ 57 % with respect to the parent ZrNiSn alloy.