Emission-color change caused by photoredox reactions of europium ions in Ba3MgSi2O8

Ba3-xEuxMgSi2O8 (0 <x <= 0.20) showed Eu3+ -derived orange emission under near-ultraviolet light. After the photostimulation using a Xe-arc lamp, the emission color turned purple because blue-emission centers arose within it. The following heat treatment reverted the emission color back to the original. From the excitation spectrum, the blue emission was assigned to Eu2+ ions those had not been identified before the photostimulation, which indicates that the photoreduction of Eu3+ caused the observed emission-color change. When x = 0.01, the most intense blue emission was induced by the photostimulation. Further addition of Eu ions lead to a decrease in the induced blue-emission intensity.