Structural phase transformation and the light-switching photochromism-related emission modulation in Eu3+-doped strontium stannates

Abstract

We investigated the photochromic and related photoluminescence modulation behaviors in Eu3+-doped strontium stannate compounds over a wide doping range. The Sr2SnO4 (n = 1 for SrO(SrSnO3)n) phase, which was dominant at low dopings, was transformed gradually into SrSnO3 (n = infinity) and Sr3Sn2O7 (n = 2) phases at higher dopings, probably due to the formation of defects by the substitution of Eu3+ to Sr2+ and Sn4+. In spite of the structural phase transformation, the PL intensities increased gradually as the nominal Eu3+ concentration increased to 0.4. After ultraviolet light irradiation, the color of our samples changed from white to gray, and the PL intensity decreased significantly. More interestingly, the reduced emission intensity of Eu3+ in the UVirradiated samples was restored by visible-light irradiation. The mechanism underlying the correlation between the PC and PL modulation behaviors was discussed with regard to the defect states induced by the Eu3+ doping.