Influence of modifier oxide on Spectroscopic properties of Ho3+: V4+ co-doped Na2O-SiO2-ZrO2 glasses

Na2O-SiO2-ZrO2 glasses co-doped with variable concentrations of Ho3+: V4+ have been synthesized, characterized by different techniques and finally their luminescence characteristics were investigated. The EDS spectra of the glass samples indicate all the elements are intact in the final composition of prepared glass. The infrared and Raman spectral studies are carried out and the existence of conventional structural units are analyzed. The ESR and optical absorption spectra indicated that a considerable proportion of vanadium ions do exist in V4+ state in addition to V5+ state. The absorption and emission spectra of Ho3+ ions were characterized using J-O theory. The radiative transition probabilities and branching ratio were evaluated from luminescence spectra. The analysis these results indicated the highest values of radiative probabilities and branching ratios for the green emission transition viz., 5S2 → 5I8 transition among various other transitions of Ho3+ ions. However, the presence of higher concentration of V2O5 in the glass matrix seems to be a hindrance for getting the high luminescence efficiency especially in the red region.