Inspecting the electronic structure and thermoelectric power factor of novel p-type half-Heuslers

In line for semiconducting electronic properties, we systematically scrutinize the likely to be grown half-Heusler compounds XTaZ (X = Pd, Pt and Z = Al, Ga, In) for their stability and thermoelectric properties. The energetically favored F-43m configuration of XTaZ alloys at equilibrium lattice constant is a promising non-magnetic semiconductor reflected from its total valence electron count (N_V = 18) and electronic structure calculations. Alongside mechanical stability, the dynamic stability is guaranteed from lattice vibrations and the phonon studies. The energy gaps of these stable Ta-based materials with Z = Ga are estimated to reach as high as 0.46 eV when X = Pd and 0.95 eV when X = Pt; however, this feature is reduced when Z = Al/In and X = Pd/Pt, respectively. Lattice thermal conductivity calculations are achieved to predict the smallest room temperature value of K_L = 33.6 W/K (PdTaGa) and 38.0 W/mK (for PtAlGa) among the proposed group of Heusler structures. In the end, we investigated the plausible thermoelectric performance of XTaZ alloys, which announces a comparable difference for the n-type and p-type doping regions. Among the six alloys, PtTaAl, PtTaGa and PtTaIn are predicted to be the most efficient materials where the power factor (PF) elevates up to ~ 90.5, 106.7, 106.5 mW/(K²m), respectively at 900 K; however the lower values are recorded for PdTaAl (~ 66.5), PdTaGa (~ 76.5) and PdTaIn (~ 73.4) alloys. While this reading unlocks avenues for additional assessment of this new class of Half Heuslers, the project approach used here is largely appropriate for possible collection of understandings to realize novel stable materials with potential high temperature applications.