Long persistent luminescence and blue photochromism in Eu2+-Dy3+ co-doped barium silicate glass ceramic phosphor

Abstract

Eu2+-Dy3+ co-doped barium silicate glass was prepared by a melt quenching method and cerammed at various temperatures between 800 and 1250 °C to obtain the glass ceramic (GC) persistent phosphors. The crystal phase of Ba5Si8O21 was primarily precipitated in the GC samples. The GC sample cerammed at 1250 °C (GC1250) exhibited the longest persistent luminescence over 16 h until the luminance becomes 2 mcd/m2. The color of GC1250 sample was changed from white to blue after UV light illumination, and then bleached efficiently by red light (660 nm) illumination or heat treatment at 200 °C. From thermoluminescence (TL) glow curve measurements, four different TL glow peaks were observed at 191 K, 278 K, 446 K, and 494 K. On the other hand, after red-illumination following UV-illumination, the TL intensity of the only 446 K-peak was selectively decreased in the TL glow curve. It was shown that the blue photochromism of GC 1250 sample is due to an electron trapping defect strongly related with this glow peak.