Optical and EPR studies of zinc phosphate glasses containing Mn2+ ions

A set of glass samples with composition based on ternary 50P 2 O 5 –30Na 2 O–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 2+ as probe. Glass compositions (100- x )PNZ: x Mn (0.01 ≤ x ≤ 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 g ), XRD analysis identified the non-crystalline arrangement, compatible with glass structure. Raman spectra of PNZ: x Mn samples showed that the successive increase in Mn 2+ content leads to rise of vibrational modes assigned to phosphate Q 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 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 3+ . Additionally, UV–Vis, PL and EPR data showed that Mn 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 2+ and PNZ glass network.