Insight into physical properties of lutetium-based double half-Heusler alloys LuXCo2Bi2 (X = V, Nb and Ta)

Based on the density functional theory, the double half-Heusler alloys LuXCo₂Bi₂ (X = V, Nb, and Ta) were studied to predict their structural, thermodynamic, thermoelectric, and optical characteristics. All the considered alloys are thermodynamically stable and have semiconductor behavior with indirect band gaps of 0.62, 0.75, and 0.8 eV for LuVCo₂Bi₂, LuNbCo₂Bi₂, and LuTaCo₂Bi₂, respectively. The investigated compounds exhibit semiconducting behavior with energy gaps below 0.8 eV. The impact of heat and pressure on thermodynamic coefficients was evaluated, and the influence of charge carriers on the temperature-dependent properties was studied using the semi-classical Boltzmann model. The studied compounds were characterized by their low lattice thermal conductivity at room temperature and low thermal expansion coefficient. These alloys exhibit substantial absorption coefficients in the ultraviolet (UV) light region, high optical conductivity, and high reflectivity in the visible light region, making them highly appealing materials for applications in the energy and electronics sectors.