Power Factors of p-type Half-Heusler Alloys ScNiBi, YNiBi, and LuNiBi by <i>ab initio</i> Calculations
M. Winiarski, Kaja Bilińska
Abstract
Electronic structures and transport properties of RENiBi materials, where RE is Sc,Y, and Lu, were investigated with the density functional theory methods. The results of the Seebeck coefficient, electrical conductivity, and power factor obtained for YNiBi are in good accordance with available experimental data. The effective masses of hole-like carriers in RENiBi compounds are expected to be relatively low (0.24-0.36), and decrease with an increasing atomic number of the RE component. The longest relaxation time of carriers, estimated within the deformation potential theory, is expected for LuNiBi. However, this material revealed the narrower band gap, which limits the thermoelectric performance. Although the room temperature power factor reaching 2.5 mW/(K 2 m), obtained for optimally p-doped LuNiBi, is lower than the recent predictions for YNiSb and LuNiSb, the results presented in this work may encourage further experimental efforts in band engineering for Bi-based half-Heusler thermoelectric materials.