Transparent glass ceramic containing Er3+:CaF2 nano-crystals prepared by sol–gel method

Er3+ doped SiO2-CaF2 transparent glass ceramic was prepared by sol-gel method. The microstructural evolution of the samples was studied with X-ray diffraction (XRD), transmission electron microscopy (TEM), and infrared spectra (IR). After heat-treatment at 900 degrees C, the Si-OH bonds and other organic groups were basically eliminated. The CaF, crystallites in the sample heat-treated at 900 degrees C are 10-20 nm in size, distributed homogeneously among the amorphous silica matrix. The efficient upconversion emission for Er3+4F9/2 -> I-4(15/2) transition was recorded under 980 nm excitation, which could be ascribed to the incorporation of Er3+ ions into the CaF2 nano-crystals with low phonon energy. (c) 2007 Elsevier B.V. All rights reserved.