Properties and mechanism of photochromism in reduced calcium aluminate glasses

Abstract

Calcium aluminate glasses melted in graphite crucibles were found to show photochromism. Upon exposure to ultraviolet radiation, broad absorptions with an apparent peak of around 2 eV and a shoulder around 3.5 eV were induced, and after interruption of the light illumination both bands faded at room temperature. A distinct photobleaching effect was observed in the fading process. Two kinds of electron-paramagnetic-resonance signals, one symmetric and the other asymmetric, were induced near g=2 by exposure to radiation. The growing and fading behaviors of the symmetric and asymmetric components were parallel to those of the 2-eV and 3.5-eV band, respectively. It is strongly suggested that the photochromism originates from an electron trapped at the site of oxygen vacancy surrounded by Ca2+ ions produced in graphite crucibles during melting under strongly reducing conditions.

Ultraviolet-radiation-induced structure and long-lasting phosphorescence in Sn2þ—Cu2þco-doped silicate glass

“…The negative g shift (g 2 g e ; where g e is the value for free electron, 2.0023) suggest the center to be of trapped electron type. Hosono et al [14] found a photochromic phenomenon in a calcium aluminate glass melted under a reducing atmosphere. Two absorption bands at around 2 and 3.5 eV were observed with ultraviolet radiation, and disappeared after removal of UV light at the room temperature.…”

Work Function of a Room‐Temperature, Stable Electride [Ca24Al28O64]4+(e–)4

“…However, C12A7 has completely different physical and chemical properties that distinguish it from the rest of its family members. For example, it can form a glass phase, [1] its crystal lattice hosts unusual anion species, [2][3][4][5] it exhibits fast oxygen-ion conduction, [6] and its volume expands by ca. 10 % when crystallized from a melt.…”

Long lasting phosphorescence of Eu2+ in reduced SrO–B2O3 glasses

“…The raw materials were SrCO 3 The density of the glasses was measured by employing the conventional Archimedes' principle with kerosene as an immersion liquid. Photoluminescence (PL) excitation spectra were measured on a HITACHI F-4500 Spectrofluorometer equipped with monochromator and 150 W Xe lamp.…”

“…Hosono et al observed the photochromism phenomenon in calcium-aluminate glasses prepared in reduced atmosphere [3], basing on which the Tb 3+ -activated LLP glasses were synthesized [4]. Similarly, LLP phenomenon has also been reported in another impurity-doped photochromism glasses, for example, Tb 3+ -or Mn 2+ -doped zinc borosilicate glasses [5,6].…”