Effect of magnetic ion, Fe3+ on the structural and dielectric properties of Oxychloro Bismuth Borate Glasses

Abstract

The glasses with composition xFe2O3(55-x) B2O310Bi2O325BaO10LiCl where x = 0.0, 5.0, 7.0, 10.0, 12.0 and 15.0) are produced via melt quenching technique. X-ray diffraction (XRD), Energy dispersive spectrum (EDS), Electron paramagnetic resonance (EPR) spectra, dielectric measurements, ac conductivity, equivalent circuit analysis, modulus analysis, dc conductivity, UV-VIS-IR spectra (using Diffused Reflectance Spectroscopy, DRS), differential thermal analysis (DTA) and Mössbauer spectra have been investigated for the synthesized glass system. The amorphous nature of as prepared glasses has been confirmed by XRD profiles. EPR spectra confirms presence of Fe3+ ions in distorted octahedral coordination and supported by UV–Vis absorption bands. The hyperfine parameters from the Mössbauer spectrum indicates that iron mainly exists as Fe3+ ions and in octahedral coordination. Dielectric constants ε′, ε″ and tanδ were found to show similar behavior and decrease with increasing frequencies. The presence of relaxation phenomena was revealed from the transition in Tangent Loss (tanδ) for compositions x = 12 and x = 15. Modulus analysis and impedance spectroscopy exhibited non-Debye type relaxation phenomena and the shifting of peaks of M″ towards higher frequency with increase in temperature. Nyquist's plot was fitted using Electrochemical Impedance Spectroscopy (EIS) software and equivalent circuit was found to hold a series combination of a capacitor with a constant phase element and a resistor connected in parallel confirmed the grain boundary effects only. Variation in ac conductivity with frequency for all samples follow Jonscher's power law and frequency exponent parameter “s” is used to analyze conduction mechanism by different conductivity models. Variation of dc conductivity with temperature confirms semiconducting behavior of prepared glasses and no deviation in linearity of Arrhenius plot depict ionic conduction mechanism principally. Optical band gap obtained from DRS is found to be in range 2.05–3.42 eV and decreases with increase in iron content.