Influence of Mn2+ ions on optical and electrical properties of Sb2O3 mixed lithium fluoro borophosphate glasses

Glasses with composition of (20-x)LiF-10Sb2O3-10B2O3-60P2O5:x MnO (0< x <0.5 mol%) were synthesized. The non-crystalline nature of the samples was confirmed by XRD analysis and the glass forming abilities were analyzed by DTA studies. The compositional dependence of various structural vibrational units was analyzed by FT-IR and Raman studies. DTA, FT-IR and Raman studies suggested a higher degree of disorder in the glass network with increasing concentration of MnO up to 0.3 mol %. The reversal trend has been observed beyond 0.3 mol% suggesting an increasing polymerization causing lower degree of disorder in the glass network. The optical properties of LiF-Sb2O3-B2O3-P2O5: MnO glasses were analyzed by optical absorption, photoluminescence and ESR spectra. The observations of ESR, OA and PL spectral studies suggested that the gradual increase of octahedral Mn2+ ions with the increase in the concentration of MnO up to 0.3 mol%. At higher concentration i.e. above 0.3 mol% of MnO, there was a reduction in the concentration of octahedral Mn2+ ions. The electrical properties of the glass samples were studied by both DC and AC conductivity studies. The dielectric dispersion analysis was also performed on the prepared glass samples. The results of these studies indicated that there is a mixed conduction (both ionic and polaronic) and the polaron hoping seems to prevail over ionic conduction in the glasses containing MnO less than 0.3 mol%. The increase in space charge polarization is responsible for enhanced values of dielectric parameters and AC conductivity for all frequency and temperature ranges.