Optical and EPR studies of zinc phosphate glasses containing Mn.sup.2+ ions

A set of glass samples with composition based on ternary 50P.sub.2O.sub.5-30Na.sub.2O-20ZnO (PNZ) matrix doped with different MnO contents was prepared via melt-quenching technique. Thermal, structural and spectroscopic properties were investigated by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), Raman spectroscopy, UV-visible absorption, photoluminescence (PL) and by electron paramagnetic resonance (EPR) using Mn.sup.2+ as probe. Glass compositions (100-x)PNZ:xMn (0.01 [less than or equal to] x [less than or equal to] 1.0 in mol% of MnO) were characterized as glasses after careful analysis of the thermal and structural data. While DSC curves show the presence of the glass transition phenomenon (T.sub.g), XRD analysis identified the non-crystalline arrangement, compatible with glass structure. Raman spectra of PNZ:xMn samples showed that the successive increase in Mn.sup.2+ content leads to rise of vibrational modes assigned to phosphate Q.sup.1 units, suggesting the breakdown of phosphate glass network chains. UV-Vis absorption spectra of glasses presented absorption bands centered at 250, 318, 341, 358 and 408 nm attributed to the Mn.sup.2+ electronic transitions. Glass samples containing above 0.06 mol% of MnO presented a broadband absorption centered at 511 nm assigned to the presence of traces of Mn.sup.3+. Additionally, UV-Vis, PL and EPR data showed that Mn.sup.2+ ions are occupying octahedral arrangements. Besides, EPR results suggest that the increase in MnO concentration influences on the EPR signal and hyperfine splitting constant suggests the presence of a moderately ionic bond between Mn.sup.2+ and PNZ glass network.