Unravelling the structural, electronic, mechanical and thermoelectric properties of half-Heusler alloys NaYX (X = C, Si, Ge, Sn)

We investigate the structural, electronic, and thermoelectric properties of the newly designed half-Heusler (hH) alloys NaYX (X = C, Si, Ge, Sn) using first-principles methods combined with Boltzmann transport theory. Our results indicate that the hH alloys are chemically, mechanically, as well as dynamically stable. The electronic calculations suggest that all the alloys are direct bandgap semiconductor with a bandgap of NaYC (0.52 eV), NaYSi (0.56 eV), NaYGe (0.57 eV) and NaYSn (0.65 eV). The lattice thermal conductivities of the hH alloys are quite low (12-24 W m -1 K-1) -1 ) at room temperature. The computed figure of merit (ZT) for p-type charge carrier concentration show higher value for NaYC alloy (ZT = 0.57) as compared to NaYSi (ZT = 0.07),NaYGe (ZT = 0.27) and NaYSn (ZT = 0.42) at 1200 K, respectively. Altogether, our results indicate the potential of hH alloys for the high-temperature thermoelectric applications.