OPTICAL SPECTROSCOPY OF A SODA LIME GLASS EXCHANGED WITH SILVER

A commerical flat soda lime glass subjected to an ion exchange process with Ag+ at different temperatures for different lengths of time is i nvestigated by means of transmission electron microscopy (TEM), optica l absorption (OA) and photoluminescence (PL) techniques. Additionally, some of the samples are thermal reheated in air and in a reducing atm osphere of N-2-H-2, in order to favour the reduction of the Ag+ ions t o Ag-0. TEM and OA measurements in the exchanged glass confirm the exi stence of silver colloids of a wide range of particle size between 20 and 250 nm. The presence of these colloids and their evolution with th e exchange parameters is monitored through a characteristic broad abso rption band peaked at about 420 nm. PL experiments reveal that only in the samples exchanged with silver does luminescence appear upon excit ation in the nearby ultraviolet. Spectral analysis shows a broad emiss ion peaked at about 600 nm with a shape that does not vary to any grea t extent with temperature and exchange time. However, its intensity is very sensitive to variations in the said parameters. On the other han d the excitation spectra exhibit a broad band with three resolved peak s at about 360, 395 and 445 nm. Their origin is tentatively explained on the basis of different centres related to the silver exchanged by t he sodium in the glass.