Room-temperature emission-color switching of Ba3MgSi2O8: Eu2+ and the photochemical reaction mechanism

Eu2+-doped Ba3MgSi2O8 exhibited room-temperature photochromism by laser irradiation. Ultraviolet laser irradiation varied the emission color from blue to purple. The following blue-to-green laser irradiation restored the original blue emission. From the laser-wavelength dependence, it has been found that the observed emission-color variation started with an electron transition from a localized state above the valence band to the conduction band. The degree of the emission-color variation was determined by the number of electrons stably trapped near Eu2+ if Eu2+ ions were doped enough.