Materials design and example of long lasting phosphorescent glasses utilizing electron trapped centers

A strategy to create an oxide glass with long lasting phosphorescence (LLP) utilizing oxygen ion vacancy (VO) associated with network modifying cations as electron traps was proposed. LLP is designed by a combination of VO and multi-valent luminescent cations (Ln+). The LLP originates from a recombination of a photooxidized luminescent ion (Ln+)+ with an electron thermally released from a VO site. We found that oxide glasses exhibiting photochromism based on photochemistry of VO such as ZnO–B2O3–SiO2 glasses and reduced CaO–Al2O3 (RCA) glasses were appropriate as host glasses. These are two variants of electron-trapped centers of VO in oxides. One is F+ center trapping an electron at the site of the VO and the other F center trapping two electrons. It was demonstrated in RCA glasses that the former and the latter primarily participate to the emergence of LLP.