Compositional dependence of local vibration around rare earth ions in SiO2-PbF2 glass-ceramics

Compositional dependence of local vibration around EU3+ in SiO2-PbF2 glass-ceramics is investigated by analysing the phonon sideband associated with the Eu3+:D-5(2) <-- F-7(O) transition. Two kinds of sideband peak are observed in a high-energy region of the D-5(2) <-- F-7(O) transition. Phonon energies of these sideband peaks are about 950 cm(-1) and 250 cm(-1) Intensities of the sidebands are greatly dependent on the composition; the phonon sideband at 950 cm(-1) increases and that at 250 cm(-1) decreases with increasing SiO2 content. The calculated multiphonon relaxation rate depends only on the intensity of the sideband at 950 cm(-1). This indicates that multiphonon relaxation of the excited rare earth ion is reduced in lower-SiO2-content regions. Infrared-to-visible upconversion luminescence of Er3+ is also measured for glass-ceramics doped with Er2O3 substituted for Eu2O3 Efficient upconversion luminescence is observed at 550 nm under 800 nm excitation. The intensity of the upconversion luminescence becomes remarkably higher in lower-SiO2-content regions.