ABSTRACT
Photochromic Glass of the Ag halide phase from the glass matrix; that is, the thermodynamics of the phase separation and how it is related to the glass composition. The glass composition space for any useful photochromic performance is essentially limited to the Ag halide alkali boroaluminosilicate system. The uniquely different aspect of photochromic glasses compared to glasses that darken when exposed to light is the rapidity of its recovery after the removal from light, that is, its fading phenomenon. The major difference between the photographic emulsions and the photochromic glasses is the fate of the holes produced during irradiation. The density of cupric ions in the copper halide crystal depends on the distribution function of cupric ions between the crystal and the glass. A few transparent glasses have been observed to exhibit some degree of photochromic behavior.
