Intrinsic point defects in thermoelectric half-Heusler alloys

The single-phase half-Heusler microstructure of ZrNiSn, (Zr0.5, Hf0.5)NiSn and Zr(Ni, Co0.2)Sn alloys was found to contain a high density of Heusler lattice bands 2–7 nm wide. These nanoscale Heusler lattice bands originated from clustering of Ni and/or Co antisites via occupation of structural vacancies by excess Ni or (Ni+Co) concentrations. The presence of these lattice point defects and their subsequent clustering could result in the reduction of thermal conductivity of the half-Heusler alloys.