Effect of CeF3 addition on the nucleation and up-conversion luminescence in transparent oxyfluoride glass-ceramics

GeO2:PbO:PbF2 glasses doped with ErF3, YbF3, and CeF3 were successfully synthesized. Highly transparent doped glass-ceramics were prepared by annealing the glasses at 360 degrees C, leading to nanocomposites made of beta-PbF2 crystallites embedded into an amorphous oxide phase. The effect of CeF3 on the nucleation process was studied, revealing that CeF3, as ErF3 and YbF3, acts as seeds for beta-PbF2 heterogeneous nucleation, but with higher nucleation efficiency. Transmission electron microscopy indicates that spherical 8-nm crystallites are formed. Energy dispersive X-ray microanalysis tends to indicate that fluoride crystallites contained high concentrations of rare-earth ions, forming a solid solution Pb1-x-y-zErxYbyCezF2+x+y+z, which has been confirmed by a study of the crystallites unit cell parameter. The optical properties of the tri-doped glass-ceramics were compared to those of Yb:Er-codoped glass-ceramics. The influence of CeF3 on the Er3+ emission and on the fluorescence decay curve of the I-4(13/2) emitting level of Er3+ was studied. In glass-ceramics containing CeF3, Er3+ up-conversion fluorescence nearly vanishes at the benefit of the 1.54-mu m Er3+ fluorescence which is enhanced.