Theoretical insights on thermoelectric transport properties and optical properties of half Heusler FeTaX (X = As, Sb, Sn) for low cost energy applications

This study presents a detailed first-principles investigation of the electronic, thermoelectric, and optical properties of half-Heusler compounds FeTaX (X = As, Sb, Sn). All compounds crystallize in a cubic structure (S.G. F-43 m) with negative formation energies and phonon spectra free of imaginary frequencies, confirming their structural and thermodynamic stability. The calculated indirect bandgaps fall in the range of 0.86–0.99 eV. Thermoelectric analysis shows that FeTaSn exhibits the best performance, reaching a peak ZT value of 1.12 at 1200 K, highlighting its potential for high-temperature thermoelectric generators. FeTaSb and FeTaAs also show competitive values with ZT = 0.95 and 0.72, respectively. Optical analysis reveals significant absorption coefficients and strong dielectric responses in the visible region, particularly for FeTaSn, which combines high optical conductivity with low reflectivity. These results demonstrate that FeTaX compounds, especially FeTaSn, are promising candidates for both thermoelectric and optoelectronic applications, offering pathways toward cost-effective and sustainable energy technologies.