The effect of Er3+ and Sm3+ on phase separation and crystallization in Na2O/K2O/BaF2/BaO/Al2O3/SiO2 glasses

Thermal annealing of Sm+3 or Er+3 doped Na2O/K2O/BaF2/BaO/Al2O3/SiO2 glasses led to the precipitation of nanocrystalline BaF2 The mean crystallite sizes were in the range from 9 to 15 nm as shown by XRD line broadening Whereas glasses without rare earth oxides showed crystallites homogenously dispersed in the amorphous matrix those doped with 0 05 mol% ErF3 or SmF3 showed highly agglomerated crystals The latter was due to droplet phase separation in the rare earth doped glasses as proved by transmission electron microscopy while in the undoped glasses phase separation did not occur Furthermore the size of the droplets depended on the BaO-concentration Fluorescence emission spectra of a samarium doped sample showed higher intensities than in the glasses they were prepared from (C) 2010 Elsevier Masson SAS All nghts reserved