Effects of annealing and Al co-doping on the photoluminescence of Ce³⁺-doped silica prepared by a sol-gel process

Abstract

The photoluminescence (PL) of the sol-gel derived Ce3+-doped silica (with or without Al co-doping) annealed at various temperatures was monitored. It was found that the PL shows a variation in emission intensity (first a decrease and then an increase), band position (red shift) and band width (broadening) with an increase of the annealing temperature. In other words, solution-like PL is exhibited in low-temperature-annealed samples and, with increasing the temperature, the PL becomes more and more similar to that observed in Ce3+-doped silica prepared by chemical vapour deposition. These changes can be attributed to the annealing induced structural evolution in silica: Ce3+ ions change from coordinating with water and silanols to embedding in silica network. In addition, Al co-doping markedly enhances the emission intensity and also affects the band position (blue shift) and band width (narrowing), which can be due to the changes in the local environment induced by the addition of Al.