Effect of CeF₃ Addition on the Nucleation and Up-Conversion Luminescence in Transparent Oxyfluoride Glass−Ceramics

GeO 2:PbO:PbF 2 glasses doped with ErF 3, YbF 3, and CeF 3 were successfully synthesized. Highly transparent doped glass−ceramics were prepared by annealing the glasses at 360 °C, leading to nanocomposites made of β-PbF 2 crystallites embedded into an amorphous oxide phase. The effect of CeF 3 on the nucleation process was studied, revealing that CeF 3, as ErF 3 and YbF 3, acts as seeds for β-PbF 2 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 Pb 1 - x - y - z Er x Yb y Ce z F 2+ 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 CeF 3 on the Er 3+ emission and on the fluorescence decay curve of the 4 I 13/2 emitting level of Er 3+ was studied. In glass−ceramics containing CeF 3, Er 3+ up-conversion fluorescence nearly vanishes at the benefit of the 1.54-μm Er 3+ fluorescence which is enhanced.