Influence of La3+ ions on the structural, optical and dielectric properties and ligand field parameters of Fe3+ hybrid borate glasses

Abstract

The effect of TM/RE mixture (i.e., Fe3+/La3+) on the optical, structural and dielectric features of alkali borate glass was investigated. XRD spectra showed the successful formation of the glass matrix. The La2O3 doping as a network modifier imposed some structural modifications, such as a ∼20% growth in density, ∼15% reduction in molar volume, and an increase in the proportion of BO4 units with a decrease in NBO's ratio. The optical spectra associated with Fe3+ ions occupying the tetrahedral and octahedral sites were subjected to tunability within the visible range by La2O3 additions. Many optical and dielectric features are greatly enhanced; Such as bandgap energy, Urbach energy, linear/nonlinear refractive index, dielectric constant and dielectric loss. The metallization criterion decreased from 0.368 to 0.364 eV−1, reflecting the semiconductor nature of the samples. The nephelauxetic effect confirmed the covalent bonding nature of Fe3+ ions, consistent with the results of ESR spectra.