Improving thermoelectric properties of ZrPtSn-based half-Heusler compound by Sb doping

Bipolar diffusion appeared at high temperature leads to the performance deterioration of thermoelectric (TE) materials, and TE materials with large band gaps have high intrinsic excitation temperature, which is important for high-temperature application. Previous calculation has revealed that ZrPtSn half-Heusler has a large band gap (~ 1.0 eV) among various half-Heusler compounds, which may be a good candidate for thermoelectric generators at high temperature. In this study, the structure and TE properties of ZrPtSn1-xSbx half-Heusler compounds were studied by optimization of carrier concentration through Sb doping. With 8% Sb substitution at Sn sites, the enhanced power factor of 23 μW·cm−1·K−2 at 850 K and figure of merit (zT) value of 0.5 at 1000 K were reported in n-type ZrPtSn compounds. Further, the effect of Ni alloying in ZrPt1-yNiySn0.92Sb0.08 compounds were also investigated. With the strong point defect scattering for phonons, the lattice thermal conductivity is decreased by ~ 40% at room temperature compared with that of unalloyed compounds. However, due to the depressed carrier mobility, the final zT does not show much superiority with ZrPtSn0.92Sb0.08 sample.