Characterization of zinc lead-borate glasses doped with Fe³⁺ ions: optical, dielectric, and ac-conductivity investigations

The optical, dielectric response, and ac-conductivity properties for six glasses of zinc lead-borate doped with different contents of Fe³⁺ (Fe₂O₃ = 0 to 10 wt%) have been investigated. UV–Vis spectra in 190–1100 nm wavelength have been carried out. Band gaps for optical energy (E^Optical), Urbach’s energy (E_U), index of refraction (n), steepness parameter (S), energy dispersion parameter of refractive index (E_d), single-oscillator energy (E_o), the dispersion refractive index (n_o), minimum reflectance wavelength (λ_o), and oscillator strength (S_o) were evaluated. Results reveal that the indirect energy gap varies from 2.57 to 1.01 eV, while the direct energy gap takes values from 2.80 to 1.45 eV. The E_U values change from 0.232 to 0.966 eV for glasses with Fe₂O₃ = 0 and 10 wt%, respectively. Also, S and λ_o decrease with the enhancement of Fe₂O₃ content. The dielectric response and ac-conductivity of the prepared glasses were investigated by broadband dielectric spectroscopy, BDS, in the frequency range from 0.1 Hz to 10 MHz and at temperatures ranging between 300 and 430 K. Two trends of activation plot have been observed in the conductivity of the samples with low content of Fe₂O₃. Although these samples show a perfect insulation features, they obey an anomalous behavior at higher temperatures. Therefore, the investigated glasses can be applied in several optical and optoelectronic devices.