Erbium doped glass-ceramics: concentration effect on crystal structure and energy transfer between active ions

Transparent glass-ceramics have been obtained by nucleation and growth of beta PbF2 crystallites around erbium impurities in a germanate grass. Different doping levels have been used to monitor the nucleation process. The segregation of the rare earth ions in the crystalline phase and then the resulting high local doping level induces a modification of the lattice parameter of PbF2 evidenced on the X-ray diffraction spectra and explained with a structural model. The decay profile of the 2.7 mum transition of the erbium ions is strongly affected by the surrounding changes induced by the ceramming process. Due to the high doping level of the crystallites, a model taking into account the energy transfers is necessary to fit the decays. Polycrystalline samples of erbium doped PbF2 have been synthesised in order to compare with the observation in the glass-ceramics. The variations occurring in the transients are compared with the structural modifications accompanying the local concentration changes. (C) 2001 Elsevier Science B.V. All rights reserved.