Mechanisms of Up-Conversion Luminescence in Glass-Ceramics Containing Er:PbF2 Nanocrystals

Transparent oxyfluoride germanosilicate glass-ceramics containing Er:PbF2 nanocrystals is synthesized on the basis of SiO2–GeO2–PbO–PbF2 initial glass doped with Er2O3. The glass-ceramics is characterized by yellow-green luminescence, the intensity of which is ~12-times higher than that for the initial glass. The redistribution of the intensity between green and red emission bands after the glass heat-treatment is explained using data of the lifetime measurements for six excited states of Er3+ ions from 4I11/2 to 2H11/2. A substantial increase of the lifetime of the 4F9/2 state (from 0.6 to 71 μs) is detected for the glass-ceramics as compared to the initial glass. UV up-conversion luminescence is observed for the glass-ceramics. The mechanisms of the up-conversion for 11 emission lines in the UV, blue, red, and deep-red spectral regions are discussed.