Variable Transmission Silicate Glasses Sensitive to Sunlight

Abstract

The process of variable transmission in silicate glasses has been accomplished by optically pumping color centers by electron transfer from europium (II) or cerium (III) which absorb sunlight at higher energies than the color center. Absorbed energy quickly pumps the visible color center band to a maximum. Upon removal of activating light, the visible color spontaneously decays.

Glass-Ceramics and Photo-Sitalls

“…For glasses, the changes under the influence of ultraviolet light or other radiation of a high energy are slow and irreversible at room temperature. Cohen and Smith [621][622] produced photochromic silicate glasses sensitized with Ce and Eu additions. Although these glasses are capable of darkening and discoloring very rapidly, they do show fatigue, i.e., a weakening of the photochromic effect after repeated cycles.…”

Purple photochromism in Sr2SnO4:Eu3+ with layered perovskite-related structure

“…Here, PC is a reversible change in color of materials under light irradiation, and it has application that includes rewritable copy papers, smart windows, optical filters, and photoswitchs. 5,6 Especially, inorganic PC materials are expected to be used in high density optical memory devices in conjunction with small semiconductor laser diodes, because of their excellent thermal stability and chemical resistance. 7 Although some inorganic oxides, such as WO 3 , MoO 3 , TiO 2 , and BaMgSiO 4 , display PC, [8][9][10] perovskite oxides which exhibit PC are particularly attractive because they can be used as multi-functional materials.…”

The Properties of Photochromic Materials

“…Thus as the product ¢1'. q3 (11) increases, the optical density attainable at the read-out wavelength is reduced.…”

“…Photolysis yields elemental silver which may subsequently recombine with the halogen. Cohen and Smith describe glasses containing cerium Ili and europium 11 [11]. Electrons released from these ions produce colour centres in the matrix.…”