First-principles calculations to investigate the oxygen deficiency effect on optoelectronic and mechano-thermoelectric properties of BaTiO3-δ (δ = 0, 0.5, 1)

Abstract

In our study of cubic perovskite materials, we employed the plane wave full-potential linearized augmented plane wave (FP-LAPW) method, grounded in density functional theory (DFT), as implemented in the WIEN2k software package, to determine the crystallographic, electronic, and optical properties of ${\text{BaTiO}}_{3-\delta }$ ($\delta$ = 0, 0.5, 1) compounds. Various GGA methods treat the potential for exchange and correlation. Barium titanate ${\text{BaTiO}}_3$ is well-known for its interesting electronic properties, particularly its ferroelectric behavior. The oxygen deficiency in this material changes their electronic behavior BaTiO₃, BaTiO_2.5, and BaTiO₂ are promising materials for optical applications in the visible and UV spectra. Furthermore, as oxygen deficiency increases, hole mobility increases as well, enhancing both the optical and electrical conductivities. BaTiO₃ exhibits typical insulating behavior with a well-defined band gap equal to 1.84 eV by GGA method. BaTiO_2.5 shows characteristics of a semiconductor or a narrow-gap insulator equal to 0.37 eV by GGA method, with an increased density of states near the Fermi level, and BaTiO₂ displays metallic behavior. Finally, based on the results obtained using both methods, it can be concluded that the band gap energy is inversely proportional to the oxygen vacancy concentration.