The Second Annealing Process Of Photochromic Glasses - A New Approach To An Old Question

It is possible to change the photochromic properties of a silver halide or cuprous halide microcrystals containing glass by a second annealing step at a temperature below Tg of the glass and below the melting point of the crystals. UV-VIS spectroscopic measurements indicate a decrease of the excitonic peaks of CuBr or CuCl microcrystals with a minimum value at a second annealing in the range 350-400 deg C. The intensity of the excitonic peak is also a function of annealing time and cooling rate. With a decrease in intensity of excitonic peaks the darkening by ultraviolet irradiation of such treated samples reduces simultaneously.