Thermal effects on optical properties of silver ruby glass

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O·10 CaO·74 SiO₂ mol%) glass doped with 0.11 and 0.35 wt.% silver are investigated. Heating treatments are carried out in a temperature range between 400 and 575 °C for times ranging from 30 to 300 min in different atmospheres and cooling rates. The starting glasses show a colourless and transparent appearance, but after thermal treatments under a reducing atmosphere become coloured, confirming the presence of silver colloids related to the 410-nm absorption band. On the other hand, the main effects of thermal treatments on the PL spectra concern those from samples treated in a reducing atmosphere. Thus, the intensity of both excitation and emission spectra chiefly diminishes in the 220–230 nm and 325–350 nm ranges, respectively. In addition, time-resolved spectra show the main ultraviolet (UV) emission centred above 330 nm upon excitation with 228-nm light. In contrast to the starting glass, we notice no shift or even slight shifts of the peak position to longer wavelengths with increasing delay time after pulse excitation, even for delay times as short as 0.01 ms. The results are discussed on the basis of transitions in which Ag⁺ ions are involved.