Coloration and Photochromic Properties of Glasses in the BaO–PbO–Al2O3–B2O3 System

A systematic spectrophotometric study of the compositions of photochromic glasses in the BaO–PbO–Al₂O₃–B₂O₃ system is performed for different combinations of photochromic additives. It is revealed that the chosen composition of the base glass facilitates the formation of colloidal silver particles, even though silver is involved in any combination of photochromic additives. This is especially true for a low content of halogen ions [1 wt % (Cl^– + Br^–)] at the concentration ratio [Ag]/[Hal] = 0.33. As a result, the glass changes to a reddish brown color and does not exhibit photochromic properties. An increase in the halogen concentration in the range [Ag]/[Hal] = 0.07–0.33 results in a decrease in the amount of colloidal silver particles. Most likely, this is accompanied by an increase in the content of the silver halide phase; that is, the necessary content of the photosensitive phase is provided to manifest the photochromic effect in the studied glass.