Study of Structure and Li<sup>+</sup> Ions Dynamics in Presence of Fe<sub>2</sub>O<sub>3</sub> in Bi<sub>2</sub>O<sub>3</sub>∙B<sub>2</sub>O<sub>3</sub> Glasses

Abstract

Glasses having composition xLi2O∙(30-x)Fe2O3∙20Bi2O3∙50B2O3 (0 ≤ x ≤ 30, in mol%) have been prepared using normal melt-quench technique. The variation in density and molar volume with composition has been investigated in terms of the structural modification that takes place in the glass matrix on decreasing Fe2O3. Infrared spectra of these glasses were recorded over continuous spectral range (400-4000 cm-1) in an attempt to study their structure systematically. IR spectra show that with increase in Li2O/Fe2O3 ratio there is formation of more structural units (e.g. [FeO4/2]-Li+) in the glass network. Bi3+ cations are present as [BiO6] octahedral units and acts as modifier in this glass system. Further, the effect of transition metal ions (iron) on the dynamics of lithium bismuth borate glasses has been studied in the frequency range of 20 Hz - 1 MHz and in the temperature range 240 – 350 °C using impedance spectroscopy. Possible conduction mechanisms are discussed. Various AC and DC electrical and dielectric parameters have been calculated and analyzed. The results show that the contribution of electronic conduction towards conductivity decreases with decreasing iron concentration, which is understood to be due to hopping of electrons from Fe2+→Fe3+. The frequency dependent conductivity has been studied using both conductivity and modulus formalism. The absence of maximum observed in dielectric permittivity in the temperature and frequency range studied, indicate the non-ferroelectric behavior of the glasses.