Influence of Al3+ ions on self up-conversion in Ho3+ doped lead silicate glasses

• PbO–Al2O3–SiO2:Ho2O3 glasses with varying concentration of Al2O3 were synthesized.
• Optical absorption, luminescence spectra and decay profiles were recorded.
• The intensity of all Ho3+ emission bands increased with increasing Al2O3 content.
• Increase is attributed to declustering of Ho3+ ions by Al3+ ions and self up-conversion.

PbO–Al2O3–SiO2:Ho2O3 glasses containing varying concentration of Al2O3 were synthesized. Some pre-structural information of the glass network is obtained using IR spectra. Optical absorption, luminescence spectra and their decay were recorded at ambient temperature. The emission spectra exhibited intense bands corresponding to 5F3 → 5I8, 5F4 + 5S2 → 5I8, 5F5 → 5I8 and 5F4 → 5I7 transitions of Ho3+ ions. The intensity of all these bands showed an enhancement with increasing Al2O3 content. Such increase is caused by decrease of luminescence quenching due to de-clusterization of Ho3+ ions by Al3+ ions in the glass network. In addition, self up-conversion due to 5F5 → 5I8 transition is predicted to populate additionally 5F2 and 5F4 + 5S2 levels and contribute to enrich the green emission. Such up conversion is quantitatively explained using rate occupation kinetics equations and transition probabilities.