Effect of Yb3+ ions content on crystallization of NaF-CaF2-Al2O3-SiO2 oxyfluoride glasses

The crystallization, phase and grain distribution in Yb3+ ions doped NaF-CaF2-Al2O3-SiO2 glass-ceramics were studied and determined by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Apparent activation energy E-a was obtained by Ozawa equation. The result shows that, E-a decreases with increasing of Yb3+ content, which indicates that introducing Yb3+ ions enhances the crystallization ability of the glass and promotes the precipitation of crystal phase from the glass. During the crystallization, Ca0.8Yb0.2F2.2 (0.8CaF(2)center dot 0.2YbF(3)) solid solution phase precipitates from the glasses, which is considered as partial Yb3+ ions taking the place of Ca2+ in CaF2. The spherical Ca0.8Yb0.2F2.2 micro-crystal grains with about 10-20 nm size distribute uniformly in the structure of the glass-ceramics. (C) 2011 Elsevier B.V. All rights reserved.