Enhanced visible emissions of Pr³⁺-doped oxyfluoride transparent glass-ceramics containing SrF₂ nanocrystals

The Pr³⁺-doped oxyfluoride transparent glass and glass-ceramic (GC) with the composition of 41SiO₂ + 10Al₂O₃ + 25.5LiF + 23SrF₂ + 0.5Pr₂O₃ were prepared and investigated their optical and luminescence properties. The formation of SrF₂ nanocrystals in GC has been confirmed by X-ray diffraction (XRD) and transmission electron micrographs (TEM). The Fourier transform infrared spectroscopy (FT-IR) studies were used to examine the network structure characteristics of silicates in the glass matrices. The XRD and TEM results suggest that the Pr³⁺ ions are progressively incorporated into the SrF₂ nanocrystals in the GC with increase in time of thermal treatment at 650 °C, corresponding to the first crystallization temperature of the glass. The obtained visible emissions of Pr³⁺-doped GC are several times enhanced than that in the glass and the lifetime of the ³P₀ level of the Pr³⁺ ions in glass and GC are found to be 7 and 12 μs, respectively. Therefore, the enhanced visible emission and lifetimes in GC are due to the incorporation of Pr³⁺ ions into the lower phonon energy of SrF₂ nanocrystals in the GCs. Moreover, the smaller difference in ionic radius between the added trivalent ions (Pr³⁺) and Sr²⁺ induces the larger enhancement of luminescence intensity in the GC. Hence, these enhanced visible luminescence properties indicate that the present glass and GC could be useful for photonic device applications.