Crystallization and fluorescence properties of Nd3+-doped transparent oxyfluoride glass ceramics

Nd3+-doped transparent oxyfluoride glass ceramics containing CaF2 were prepared through controlled crystallization of melt-quenched glass. X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) observation revealed the precipitation of CaF2 crystallites with about 13 nm in size among the glass matrix after heat-treatment at 650 °C for 2 h. Non-isothermal investigation on CaF2 crystallization kinetics showed that the apparent activation energy Ea and Avrami exponent n are about 310 kJ/mol and 1.23, respectively, indicating the crystallization a diffusion controlled growth process with zero nucleation rate. Fluorescence measurements exhibiting a stronger emission in the glass ceramics than in the precursor glass, together with the fluorescence decay results and energy dispersive X-ray spectroscopy (EDS) analysis, evidenced the incorporation of Nd3+ into CaF2 during crystallization.