Experimental optical analysis and DFT study of the electronic, thermoelectric and optical characteristics of a co-doped perovskite system

Abstract

Experimental and theoretical investigations of the electronic, thermoelectric and optical properties of Ba_0.85Sr_0.15Ti_0.85Zr_0.15O₃ ceramic are presented via density functional theory (DFT) calculations performed using the generalized gradient approximation (GGA) with a plane-wave pseudopotential approach. This interesting combined analysis provides valuable insights into the potential of the material for advanced functional applications. The electronic structure analysis reveals that Ba_0.85Sr_0.15Ti_0.85Zr_0.15O₃ exhibits a semiconducting behavior with a band gap energy of approximately 2.52 eV. The partial density of states analysis reveals that the O “p” orbitals dominate the valence band, while the Ti and Zr “d” orbitals primarily contribute to the conduction band. The thermoelectric properties examined between 300–1200 K show a consistently positive Seebeck coefficient, confirming p-type conduction. The material also demonstrates a notable dimensionless figure of merit at 300 K, indicating excellent thermoelectric performance near room temperature. These features suggest that Ba_0.85Sr_0.15Ti_0.85Zr_0.15O₃ is a promising candidate for ambient-temperature thermoelectric energy conversion, optoelectronic devices, and multifunctional oxide-based electronics. Experimentally, UV-visible spectroscopy yielded a direct band gap of 2.419 eV and an Urbach energy of 0.784 eV, reflecting a moderate level of localized states within the band gap. The extinction coefficient spectrum reveals pronounced wavelength-dependent features, with enhanced absorption extending from the UV to the visible-red region (650–720 nm), indicating the formation of defect-related and polaronic states that effectively narrow the optical band gap.