Outstanding figure of merit at high temperature for DFT-based predicted double perovskite oxides, Ba2GaXO6 (X = V, Nb, Ta)
Thermoelectric materials with a high figure of merit (ZT) are highly demanded for a sustainable solution to the energy crisis. In this study, we have predicted three new double perovskite oxides (DPOs), Ba2GaXO6 (X = V, Nb, Ta), with high ZT values using density functional theory (DFT) calculations and investigated their structural, electronic, thermoelectric, and mechanical properties. The electronic properties, such as electronic band structure, density of states (DOS), and charge density mapping, are used to disclose the conductive nature, chemical bonding within these compounds, which exhibit direct band gaps of 0.924, 2.354, and 3.279 eV for Ba2GaVO6, Ba2GaNbO6, and Ba2GaTaO6, respectively, as calculated using the TB mBJ potential. The thermoelectric performance of the new DPOs, Ba2GaXO6 (X = V, Nb, Ta), was assessed using the BoltzTrap2 code, which yielded outstanding ZT values of 2.36, 1.78, and 1.91 at 1500 K for Ba2GaVO6, Ba2GaNbO6, and Ba2GaTaO6, respectively, indicating their potential for waste heat management. The high ZT values are attributed to an ultra low lattice thermal conductivity, arising from strong scattering of acoustic and optical phonon modes. The changes in thermoelectric parameters with temperature were analyzed and explained.