Long luminescent glass: Tb3+-activated ZnO–B2O–SiO2 glass

Abstract It has been found that zinc borosilicate glasses 60ZnO–20B 2 O 3 –20SiO 2 doped with 0.2 mol% Tb 2 O 3 exhibit phosphorescence after exciting with 254 nm light. This phosphorescence arises from f–f transitions of Tb 3+ ions and is observable by the eye, in the dark for up to 1 h after stopping the UV-illumination. Electron spin resonance (ESR) measurements show that electron trapping centers, associated with Zn ions, are formed by the UV irradiation and the phosphorescent centers decay after the irradiation was stopped. We suggest that this UV induced center is the photo-induced electron trap, which serves effectively as an electron donor, in the dark.