Rare-earth doped oxyfluoride glass-ceramics and fluoride ceramics: Synthesis and optical properties

Ultra-transparent glass-ceramics are synthesized in the GeO2-PbO-PbF2 system by rare-earth heterogeneous nucleation of PbF2. The influence of YbF3 on the nucleation process is studied through differential thermal analysis (DTA) and the morphology is observed by transmission electron microscopy (TEM). The optical properties of the glass-ceramics are compared to those of the starting glass as well as to those of a PbF2 single crystal. Thanks to the RE segregation inside the PbF2 crystallites, the optical characteristics of the glass-ceramics are found to be equivalent to those of the single crystal. The synthesis of rare-earth doped CaF2 nano-powders, as precursors for transparent ceramics, by direct precipitation, microemulsion and mechanosynthesis is described. The different obtained powders are characterized by X-ray diffraction (XRD) and TEM and their respective morphology and purity are compared. For the powder obtained by microemulsion, the effect of annealing at various temperatures is investigated showing an increase of the particles sizes and an enhancement of the optical properties. (c) 2006 Elsevier B.V. All rights reserved.