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), Ba 2 GaXO 6 (X = V, Nb, Ta), with high ZT values using density functional theory (DFT) calculations and investigated their structural, electronic, thermoelectric, and mechanical properties. The structural stability was confirmed through the energy-volume curve, octahedral factor, Goldschmidt’s tolerance factor, new tolerance factor, formation energy, phonon dispersion spectra, and ab initio molecular dynamics (AIMD) simulations, which indicated the feasibility of synthesizing the predicted compounds. The electronic properties, such as electronic band structure, density of states (DOS), and charge density mapping, are used to disclose the conductive nature and chemical bonding within these compounds, which exhibit direct band gaps of 0.924, 2.354, and 3.279 eV for Ba 2 GaVO 6 , Ba 2 GaNbO 6 , and Ba 2 GaTaO 6 , respectively, as calculated using the TB−mBJ potential. Elastic stiffness constants C 11 , C 12 , and C 44 analysis confirms mechanical stability and ductile behavior, consistent with the ionic nature of bonding. Thermoelectric performance of the new DPOs, Ba 2 GaXO 6 (X = V, Nb, Ta), was assessed via the BoltzTrap2 code, which yields outstanding ZT values of 2.36, 1.78, and 1.91 at 1500 K for Ba 2 GaVO 6 , Ba 2 GaNbO 6 , and Ba 2 GaTaO 6 , respectively, indicating their potential for waste heat management. The high ZT values are attributed to an ultra-low lattice thermal conductivity, which is due to the strong scattering of acoustic and optical phonon modes. The changes in thermoelectric parameters with temperature were analyzed and explained. As the outcome of this study, the Ba 2 GaXO 6 (X = V, Nb, Ta) perovskites are identified as a promising thermoelectric material, providing a sustainable solution to the current energy crisis.