Alloying-induced reduction of lattice thermal conductivity in TiFeTe

The effect of selenium (Se) substitution for tellurium (Te) on the electronic structure, phonon transport, and thermoelectric performance of TiFeTe was systematically investigated using first-principles density functional theory (DFT) and semiclassical Boltzmann transport calculations. Se incorporation enhances phonon scattering and markedly suppresses lattice thermal conductivity, while exerting a negligible influence on the Seebeck coefficient. Although enhanced carrier scattering slightly reduces electrical conductivity and the power factor, alloying effectively lowers lattice thermal conductivity while retaining favorable electronic transport properties. Consequently, both p-type and n-type TiFeTe systems exhibit substantial improvements in the thermoelectric figure of merit (zT). In particular, TiFeTe_0.5Se_0.5 exhibits superior n-type thermoelectric performance with a zT value approaching 2.0 at 1200 K. These findings demonstrate that controlled alloying is an effective approach to modulate phonon transport and enhance the thermoelectric efficiency of half-Heusler compounds.