Investigation of the electronic structure, mechanical, and thermoelectric properties of novel semiconductor compounds: XYTe (X = Ti/Sc; Y = Fe/Co).

Abstract

We report the structural, mechanical, electronic, phonon, and thermoelectric properties of new XYTe (X= Ti/Sc; Y = Fe/Co) half-Heusler compounds by employing first principles based DFT computation and Boltzmann transport equations. At their equilibrium lattice constants, these alloys exhibit a crystal structure with a space group (#216) of F4̄3m and adhere to the Slater Pauling (SP) rule, while being non-magnetic semiconductors. The Pugh's ratio of TiFeTe shows that it is a ductile material, which makes it suitable for use in thermoelectric applications. On the other hand, ScCoTe's brittleness or fragility makes it less promising as a potential thermoelectric material. The dynamical stability of the system is investigated using the phonon dispersion curves obtained from its lattice vibrations. The band gaps of TiFeTe and ScCoTe are 0.93 eV and 0.88 eV, respectively. The electrical conductivity (σ), Seebeck coefficient (S), thermoelectric power factor (PF), and electronic thermal conductivity are calculated at various temperatures ranging from 300 K to 1200 K. At 300 K, TiFeTe has a Seebeck coefficient of 1.9 mV K-1 and a power factor of 136.1 mW m-1 K-2. The highest S value for this material is obtained through n-type doping. The optimal carrier concentration for achieving the highest Seebeck coefficient in TiFeTe is 0.2 × 1020 cm-3. Our study indicates that the XYTe Heusler compounds exhibit n-type semiconductor behavior.