Optical, photoluminescence, and E.S.R spectral analysis of manganese ions in phosphate glasses melted under various conditions and impact of gamma irradiation

Abstract

Glasses from NaCa fluorophosphate doped with varying MnO2 dopant (0.25, 0.50, 1.0%) and melted under different conditions were prepared by normal melting annealing technique. Collective optical, FTIR, photoluminescence, and E.S.R spectral measurements for the various MnO2-doped glasses were done. Optical spectrum of the undoped host fluorophosphate glass reveals only distinct UV absorption which is correlated to contaminated trace iron (Fe3+) ions present as impurities. The MnO2-doped glasses show the same UV absorption beside two additional bands, a small one at 410 nm which is assumed to originate from (Mn2+) ions of spin-forbidden nature and a broad visible and distinct band centered at 500 nm representing the absorption of trivalent manganese (Mn3+) ions of spin-allowed nature. The effects of varying melting conditions reveal obvious changes in the intensities of the two visible bands. FTIR spectra reveal extended vibrational peaks due to phosphate (PO4) groups with sharing of some fluorophosphate (PO3F) groups and the introduction of increasing percent of the dopant that causes minor variations in the FTIR spectra. Photoluminescence spectra reveal a broad emission band centered at about 635 nm and the intensity of the emission band increases with the increase of MnO2 content and is more distinct in glass melted under reducing conditions than that melted at normal condition. E.S.R spectral measurements were carried out to confirm the optical results indicating the existence of measurable divalent Mn2+ ions which increases in reducing conditions. The effects of gamma irradiation (6Mrad dose) on the studied spectral properties were evaluated.