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

Transparent glass-ceramics have been obtained by nucleation and growth of b eta PbF2 crystallites around erbium impurities in a germanate grass. Differ ent doping levels have been used to monitor the nucleation process. The seg regation of the rare earth ions in the crystalline phase and then the resul ting high local doping level induces a modification of the lattice paramete r of PbF2 evidenced on the X-ray diffraction spectra and explained with a s tructural model. The decay profile of the 2.7 mum transition of the erbium ions is strongly affected by the surrounding changes induced by the cerammi ng process. Due to the high doping level of the crystallites, a model takin g into account the energy transfers is necessary to fit the decays. Polycry stalline samples of erbium doped PbF2 have been synthesised in order to com pare with the observation in the glass-ceramics. The variations occurring i n the transients are compared with the structural modifications accompanyin g the local concentration changes. (C) 2001 Elsevier Science B.V. All right s reserved.