Effects of rehydration on Tb3+ spectroscopy in sol–gel glasses

Spectroscopy of sol–gel silicate glasses containing Tb3+ is used to investigate the diffusion of water from the atmosphere into annealed glass samples. In materials that are annealed to 900 °C the blue–violet 5D3 → 7FJ fluorescence is comparable in intensity to green emission from the 5D4 level. However, the 5D3 emission is reduced to ∼5% of its original strength in several hours if glasses are exposed to ambient conditions. Re-annealing restores the original intensity of the 5D3 fluorescence. The degree of fluorescence quenching is shown to depend strongly on initial preparation of the sol–gel materials and on annealing conditions.