First-principles quantum analysis of structural, optoelectronic, thermoelectric and thermodynamic properties of niobium-based pyrochlore oxides A2Nb2O7 (A = Ba, Mg, and Sr) for energy harvesting applications

Abstract

The present study employed first-principles DFT (density functional theory) computations to investigate the impact of alkaline metal substitutions on the structural, optoelectronic, thermodynamic, and thermoelectric characteristics of Nb-based pyrochlore oxides A2Nb2O7 (A = Ba, Mg and Sr). The PBE-GGA model is employed to calculate the fundamental characteristics of Nb-based pyrochlore oxides. An in-depth analysis of the energy band structures reveals that these Nb-based pyrochlore oxides are semiconductor compounds of A2Nb2O7 (A = Ba, Mg, and Sr) reveals that these Nb-based pyrochlore oxides are semiconductors. The energy bandgap values are around 0.6, 3.05, and 1.4 eV for Ba2Nb2O7, Mg2Nb2O7, and Sr2Nb2O7, respectively. Based on the observed ε2(ω) spectra, it is apparent that the A2Nb2O7 (A = Ba, Mg, and Sr) compound, exhibits a significant absorption of incident photons in the near UV region (at approximately 5.0 eV). The calculated values of n(ω) are 1.71, 1.66 and 1.63 for Ba2Nb2O7, Mg2Nb2O7 and Sr2Nb2O7, respectively. The values of ZT are 0.661, 0.998 and 0.996 for Ba2Nb2O7, Mg2Nb2O7 and Sr2Nb2O7, respectively, which make them favourite for TE device applications. The optoelectronic and thermoelectric properties of Nb-based pyrochlore oxides A2Nb2O7 (A = Ba, Mg, and Sr) indicate their potential as favorable contenders for energy-related applications. The elucidated thermodynamic properties reveal that the Nb-based pyrochlore oxides A2Nb2O7 (A = Ba, Mg, and Sr) display a high degree of thermal stability. © 2024 Elsevier B.V.