Study of thermoelectric performance and intrinsic defect of promising n-type half-Heusler FeGeW

Half-Heusler (HH) compounds are considered promising thermoelectric materials for high-temperature power generation due to their good electrical properties and thermal stability. Some new HHs with excellent thermoelectric properties are found to be p-type, the discovery of competitive n-type HH materials has been extremely challenging. Here, we report a new HH compound FeGeW through first-principles calculation, which exhibits a high ZT of 2.36 at 1000 K. Systematically studied its thermoelectric performance indicates that a large dispersion or small band effective mass of conduction band can efficiently improve the electrical conductivity of n-type FeGeW. From the calculated formation energy of intrinsic point defects, we find that positive charged Fe interstitial are found to be the dominant defect at Fe-rich/Ge-poor condition, which account for the n-type conduction. Moreover the transition levels of Fe interstitial defect is shallow, which means that this donor defect does not damage electrical conductivity and thermoelectric performance. These results not only find a new n-type HH compound FeGeW, but also are helpful for understanding the roles of point defects in FeGeW, which is expected to encourage more experimental and theoretical investigations to study this kind of n-type HH thermoelectric material and seek out strategies to optimize thermoelectric performance using intrinsic point defect.