Comprehensive investigation of Li-based novel quaternary Heusler LiTiPdZ (Z = Al, Ga, In) compounds for thermoelectric performance

Abstract

In the present article, we used Density Functional Theory and the Boltzmann transport equation to study the structural, electronic, and thermoelectric (TE) properties along with phonon dynamics of recently discovered LiTiPdZ (Z = Al, Ga, In) quaternary Heusler (QH) compounds. We applied generalized gradient approximations (GGA) for band structure and density of states (DOS) calculations. Comprehensive investigations of electronic structure reveal that an indirect band gap of 0.77 eV, 0.793 eV and 0.611 eV for LiTiPdAl, LiTiPdGa, and LiTiPdIn, is there reflecting the semiconducting nature of these compounds. We find that Pd-4d states contribute to the conduction band DOS while Ti-3d states contribute significantly to DOS near Fermi energy (EF) in both valence and conduction band. Phonon dispersion spectra show that all the studied compounds are dynamically stable, as obtained frequency is only in positive range. We have calculated thermoelectric properties up to a fairly high temperature (1600 K), to check the compatibility of these compounds for high temperature TE application. A high value of ZT (∼0.60 1600K) proposes these compounds as potential candidates for high temperature TE applications.