Effects of Ti Doping on TaFeSb Half-Heuslers Estimated by a Single Parabolic Band Model

Recent discovery of new p-type Ta_1-xTi_xFeSb-based half-Heusler thermoelectric alloy has drawn much attention due to its high thermoelectric performance, zT of ∼1.52 near 970 K. However, the electronic band parameters of TaFeSb nor Ti-doped TaFeSb have not been studied so far. Here we report the band parameters of Ta_1-xTi_xFeSb (x=0–0.16) calculated by the Single Parabolic Band model. Ti doping (x=0.12) both increases the density-of-states effective mass and non-degenerate mobility by 27 and 29 times compared to those of the pristine TaFeSb (x=0). This simultaneous increase results in weighted mobility improvement by a factor of 4000 with Ti doping of x=0.12. Based on the estimated weighted mobility and the lattice thermal conductivity, the 300 K zT of Ta_0.88Ti_0.12FeSb (x=0.12) can be further increased by 10% once the carrier concentration is appropriately tuned.