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.

[Display omitted] • Structural, optoelectronic, and thermophysical properties of Nb-based pyrochlore oxides A 2 Nb 2 O 7 (A = Ba, Mg and Sr) are investigated using ab-initio calculations. • A 2 Nb 2 O 7 (A = Ba, Mg and Sr) are narrow band semiconductors. • The ZT values for Mg2Nb2O7 [0.998] and Sr2Nb2O7 [0.996] make them favorite candidates for TE device applications. • Optical spectra show major absorption peaks for these pyrochlore oxides occur in near UV region. 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 A 2 Nb 2 O 7 (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 A 2 Nb 2 O 7 (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 Ba 2 Nb 2 O 7 , Mg 2 Nb 2 O 7 , and Sr 2 Nb 2 O 7 , respectively. Based on the observed ε 2 (ω) spectra, it is apparent that the A 2 Nb 2 O 7 (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 Ba 2 Nb 2 O 7 , Mg 2 Nb 2 O 7 and Sr 2 Nb 2 O 7 , respectively. The values of ZT are 0.661, 0.998 and 0.996 for Ba 2 Nb 2 O 7 , Mg 2 Nb 2 O 7 and Sr 2 Nb 2 O 7 , respectively, which make them favourite for TE device applications. The optoelectronic and thermoelectric properties of Nb-based pyrochlore oxides A 2 Nb 2 O 7 (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 A 2 Nb 2 O 7 (A = Ba, Mg, and Sr) display a high degree of thermal stability. [ABSTRACT FROM AUTHOR]