Structural impact of iron ions on BaBiBO4 glasses: Spectroscopic and dielectric investigations

Transparent glasses of composition 10BaO.20Bi2O3.(70 − x)B2O3.xFe2O3 (wt.%) where 0 ≤ x ≤ 2.0, were characterized by XRD and SEM. Physical, spectroscopic and dielectric properties were investigated. At higher dopant of Fe2O3, EPR results revealed that, the number of Fe3+ ions participate in the resonance is decreased by forming a new signal at g ≈ 3.015 due to increase of antiferromagnetic interaction of Fe3+ ions and/or formation of low spin Fe3+ ions in the glass matrix. With initial 0.5 wt.% doping of Fe2O3, less dense glass is formed with colloids of metallic Bi0 atoms. The absorption bands at 604 and 712 nm in F5 glass are ascribed to Bi0 and Bi+ radicals respectively. No characteristic Fe3+ absorption bands (spin-forbidden) are found. Fe2+ ions are increased at higher concentration of Fe2O3. Higher concentration of Fe2O3 is favorable for BO2O−, BO3, BiO6 and FeO6 symmetry unit leads to low band gap and high Urbach energy. By doping of Fe2O3 the dielectric parameters like dielectric constant (ε′), loss (tanδ and ac electrical conductivity (σac) are found to increase.