From Electrons to Energy Conversion: A First‐Principles Study of NbYAl (Y = Ni, Pd, and Pt) Half‐Heusler Thermoelectrics

An ab initio investigation of the structural, mechanical, electronic, and thermoelectric properties of Nb‐based half‐Heusler alloys NbYAl (Y = Ni, Pd, and Pt) is presented for high‐temperature energy conversion applications. Total energy optimization confirms that all NbYAl alloys crystallize in the thermodynamically stable half‐Heusler structure. All compounds crystallize in the stable Y3‐type half‐Heusler structure and satisfy mechanical stability criteria, exhibiting ductile behavior. Electronic structure calculations reveal direct band gaps at the X point with band gap values of 0, 0.017, and 0.133 eV for NbNiAl, NbPdAl, and NbPtAl, respectively. Thermoelectric transport properties are evaluated using Boltzmann transport theory within the constant relaxation time approximation over the temperature range of 100–1200 K. The NbPtAl alloy exhibits superior p‐type thermoelectric performance with a maximum ZT ∼0.70 at 1200 K, attributed to its large Seebeck coefficient, high power factor, and reduced lattice thermal conductivity. NbNiAl and NbPdAl shows the lower thermoelectric performance comparing to NbPtAl half‐Heusler alloy. These results highlight NbYAl alloys as promising candidates for high‐temperature thermoelectric applications.