Enhanced thermoelectric performance of Hf-doped ZrNiSn: a first principle study

In this work, we perform a systematic study on the thermoelectric properties of Zr_1-xNiSnHf_x using first-principles calculations combined with Boltzmann transport equations. The power factor of Zr_1-xNiSnHf_x increases as the temperature increases from 300 to 1200 K, because the increase in electrical conductivity is greater than the decrease in the Seebeck coefficient. The power factor of Zr_7/8NiSnHf_1/8 is larger than that of other Zr_1-xNiSnHf_x thermoelectric materials, but the thermoelectric figure of merit (ZT) is similar to that of others materials. This is due to the higher electronic thermal conductivity of Zr_7/8NiSnHf_1/8 compared to other materials. The maximum ZT of p-type (n-type) Zr_1-xNiSnHf_x is 0.98 (0.97), 0.9 (0.89), 0.83 (0.80), and 0.72 (0.73) at 300 K, 600 K, 900 K, and 1200 K, respectively, which are greater than those of the pure ZrNiSn. In conclusion, Hf-doped ZrNiSn can enhance the thermoelectric performance and are promising candidates for thermoelectric materials.

This paper uses FP-LAPW implemented in the WIEN2K code. The thermoelectric performance is calculated based on the semi-classical Boltzmann theory implanted using the BoltzTraP code. The electronic thermal conductivity (κ_e) and the carrier concentration (n) have been calculated using the density functional theory.