Correlation between the electronic structure, effective mass and thermoelectric properties of rare earth tellurides Ba2MYTe5 (M = Ga, In)

Abstract

Rare earth telluride compounds, namely Ba₂MYTe₅ (M = Ga, In), are the focus of this work due to their semiconducting nature, optoelectronic and thermoelectric properties. Their band gaps lie in the range of 1.08 to 1.36 eV, providing these compounds with opto- and thermo-electric properties. Here, we have studied the rare earth telluride single crystals of Ba₂MYTe₅ (M = Ga, In) using the full potential linearized augmented plane wave package WIEN2k. The direct band gaps were calculated using the modified Becke–Johnson approach which is in good agreement with the band gaps obtained from diffuse reflectance spectra. The density of states reveals a strong hybridization between Y 5s/4p, Ga 3d, Te 5p and Y 4d orbitals, indicative of covalent bonding. Besides, the electronic charge density contour discloses a mix of ionic and covalent bonding between the elements. We also report the thermoelectric properties studied through the temperature dependent electronic and thermal conductivities, as well as the Seebeck coefficient and the power factor using the BoltzTraP code.