An ab initio study on XRhP (X = Ti, Zr, Hf) half Heusler alloys for waste energy harvesting-based thermoelectric applications

The increasing demand for sustainable energy solutions has led to extensive research on thermoelectric materials that convert waste heat into electricity. Half-Heusler alloys are promising candidates due to their stability, electronic properties, and moderate thermal conductivity. To assess their thermoelectric potential, this study investigates the structural, electronic, mechanical, and thermoelectric properties of XRhP (X = Ti, Zr, Hf) alloys. Density Functional Theory (DFT) calculations using the WIEN2k software were employed to study structural, electronic, and mechanical properties. The BoltzTraP code was used to compute transport properties such as the Seebeck coefficient (S), electrical conductivity (σ), and thermal conductivity (κ). The Slack model estimated lattice thermal conductivity (κL), and the thermoelectric figure of merit (zT) was calculated. The optimized lattice parameters for TiRhP, ZrRhP, and HfRhP were 5.75 Å, 5.98 Å, and 5.95 Å, respectively. These alloys exhibit semiconducting behavior with band gaps of 0.85 eV, 1.44 eV, and 0.73 eV. At 1400 K, the highest zT values were 1.31, 0.70, and 1.46, with reduced lattice thermal conductivities of 0.52 W/m·K, 0.43 W/m·K, and 0.40 W/m·K, respectively, in the p-type material of XRhP alloy, highlighting their potential for thermoelectric applications.