SPECTROSCOPIC INVESTIGATIONS OF MANGANESE IONS IN MICROWAVE-PREPARED NAPO3-PBO GLASSES

The EPR spectra of microwave-prepared 70NaPO(3):30PbO glasses containi ng different weight percentages of manganese ions have been studied. T he EPR spectra exhibit a well-resolved hyperfine pattern at g(eff) app roximate to 2.0. Optical absorption, fluorescent emission and excitati on spectra of the glasses have been examined. The absorption spectrum exhibits a peak near 500 nm and this has been attributed to the spin-a llowed E-5(g) --> T-5(2g) transition of Mn3+ ions. The emission spectr um shows a band at 595 nm which has been assigned to the T-4(1g)(G) -- > (6)A(1g)(S) spin-forbidden transition of Mn2+ ions in octahedral coo rdination. Concentration quenching of fluorescence was found to occur above 0.75 wt% of Mn2+ ions. The excitation spectra exhibit four bands characteristic of Mn2+ ions in octahedral coordination. From the obse rved band positions of the excitation spectra, the crystal field param eter D-q and the Racah interelectronic repulsion parameters, B and C h ave been calculated. A structural model is proposed based on the IR, R aman and MASNMR studies according to which Mn2+ ions are likely to occ upy sites similar to Na+ ions in these glasses. (C) 1997 Elsevier Scie nce Ltd. All rights reserved.