Proton Irradiation Effect on Thermoelectric Properties of Nanostructured N-Type Half-Heusler Hf_0.25Zr_0.75NiSn_0.99Sb_0.01

Thermoelectric properties of nanostructured half-Heusler Hf_0.25Zr_0.75NiSn_0.99Sb_0.01 were characterized before and after 2.5 MeV proton irradiation. A unique high-sensitivity scanning thermal microprobe was used to simultaneously map the irradiation effect on thermal conductivity and Seebeck coefficient with spatial resolution less than 2 μm. The thermal conductivity profile along the depth from the irradiated surface shows excellent agreement with the irradiation-induced damage profile from simulation. The Seebeck coefficient was unaffected while both electrical and thermal conductivities decreased by 24%, resulting in no change in thermoelectric figure of merit ZT. Reductions in thermal and electrical conductivities are attributed to irradiation-induced defects that act as scattering sources for phonons and charge carriers.