Mobility Ratio As A Probe For Guiding Discovery Of Thermoelectric Materials: The Case Of Half-Heusler Phase Scnisb1-Xtex

Analysis of bipolar thermal conductivity might be very useful in preliminary stages of thermoelectric materials discovery. Using its product?mobility ratio between electrons and holes?it is possible to choose the most promising compound from the series and pave the correct direction of doping. Current work presents positive verification of this approach for ScNiSb, which is anticipated to show superior mobility when tuned towards n-type behavior. In agreement with expectation, the mobility increases by an order of magnitude due to rising tellurium content in the ScNiSb1?xTex series. The effect is most likely driven by change of the dominant charge carriers? scattering mechanism from ionized impurity influence to point defect and acoustic phonon interaction. Simultaneously, due to a highly anisotropic conduction band, the effective mass of the carriers rises towards the n-type regime. These two effects lead to an improved thermoelectric power factor of electron-doped samples, up to 40 ?WK?2 cm?1 at 740 K for ScNiSb0.85Te0.15. Based on this result, we suggest n-type doping for other rare-earth-based half-Heusler compounds. Representatives of this group exhibit the smallest lattice thermal conductivity in the pristine form among any half-Heusler thermoelectrics, and are anticipated to show comparably good electrical properties to ScNiSb due to their high mobility ratio in favor of electrons.