Multi color density photochromism in reduced tridymite BaMgSiO4 by wavelength of irradiation light

We have investigated the multi color density photochromism in reduced tridymite BaMgSiO4 (BMS-H) semiconductors, which can utilize green light, blue light, sunlight and ultraviolet light. It is found that BMS-H is one of visible light photochromic material with high response. BMS-H changes color from white to pink by sunlight irradiation or 405 nm light. The colored BMS-H is irradiated with 532 nm light, and the sample is substantially bleached. Furthermore, the colored BMS-H changes bright pink by 365 nm light irradiation. The pink color density of BMS-H strongly depends on the wavelength of irradiation lights. After heat treatment of 250°C for three minute in air, the sample is substantially bleached, and the bleached sample regains its color on light irradiation. BMS-H shows high reversibility in the coloring–bleaching processes. The pink color of BMS-H irradiated 365 nm light could be observed by visual confirmation after 22 days. The photogenerated colored state is comparatively stable in air at room temperature.