Sol–gel synthesis and characterisation of erbium-modified silica glasses

Homogeneous, erbium-modified, non-porous silica glasses containing about 2.4% of ions compared with Si atoms have been prepared by sol–gel process. To limit the loss of the rare earth cations in the liquids, improve the uniformity of ion incorporation and to immobilize the cations in the silica matrix, an amino functionalised silane was used. It was found to be very effective also to allow foamless sintering. Structural evolution and chemical composition of the samples during the preparation process have been monitored by Fourier-Transform Infrared and Near-IR dispersion spectroscopy. The loss of the cations in the syneresis liquid and the surface area of the samples heat treated at different temperature have been evaluated. The erbium transition 4I15/2 versus 4I13/2, related electro-luminescence at 1.54 μm, was evident in gels heat treated at 1000 °C.