Transparent Oxyfluoride Glass-ceramics Containing CaF2 Nano-Crystalline Phase

Transparent oxyfluoride tellurite glass with the composition of TeO2-SiO2-AlF3-CaO-KF system were prepared by conventional melting and annealing technique, and the transparent oxyfluoride glass-ceramics containing CaF2 nano-crystallines were obtained by controlled heat-treatment. The effect of heat-treatment schedules on the crystallization behavior and the microstructure of the glass-ceramics were analyzed by differential scanning calorimetry analysis, X-ray diffraction analysis, infrared spectrum and scanning electron microscopy. The sole CaF2 crystalline phase was confirmed, the spherical CaF2 nano-crystallines embed homogeneously among the glassy matrix after crystallization. The size of CaF2 grains grew with the increase of crystallization temperature and holding time. Te and Si atoms existed in [TeO3] and [SiO4] forms. Part of Al atoms existed in the form of [AlO4] and formed network together with [SiO4] tetrahedron. The other Al atoms acted as modifiers in the form of [AlO6]. The transmittance of glass-ceramics can reach 85 % in visible light and 90 % in infrared waveband. The novel transparent oxyfluoride tellurite glass-ceramics are excellent matrix materials in up-conversion luminescence field.