A first-principles assessment of the thermoelectric properties in half-heusler compound NbIrSn

Converting waste heat into electric power using thermoelectric materials could significantly address global energy needs. Half-Heusler compounds exhibit significant promise as thermoelectric materials suitable for high temperatures, thereby offering a potential solution to address the energy crisis. By employing density functional theory (DFT), semi-classical Boltzmann transport theory (BTE), and density functional perturbation theory (DFPT), this study thoroughly examines the structural, electronic, magnetic, phonon, mechanical, and thermoelectric properties of 18 valence electron half Heusler compound NbIrSn. Considering the presence of heavy 5d transition element Ir in our compound, all calculations are carried out with and without spin-orbit coupling (SOC). This material display both dynamic and mechanical stability, and also possess the property of ductility as indicated by Pugh's ratio and Poisson's ratio. NbIrSn is identified as non-magnetic semiconductors with indirect band gaps of 0.65 eV and it reduces to 0.63 eV when SOC is included. The different transport parameters are analyzed in relation to the chemical potential and doping concentrations for different temperatures. The lattice thermal conductivity of the material at room temperature is measured to be 13.40 Wm-1K-1 and 14.81 Wm-1K-1without and with SOC respectively. The optimal zT values for NbIrSn at 1200 K are 0.98 with p-type doping and 0.31 with n-type doping. Incorporating SOC leads to a substantial improvement, raising the optimal zT values to 1.33 for p-type doping and 0.47 for n-type doping. In conclusion, incorporating SOC is essential when analyzing the characteristics of the proposed compound. The present study highlights NbIrSn as a potentially a favorable candidate for p-type doping on high-temperature power generation.