Abstract
This paper reports frequency upconversion and intrinsic optical bistability in the Ho3+/Yb3+ co-doped gadolinium tungstate phosphor. The structural analyses confirm the formation of two monoclinic crystalline phases iso-structural to Gd2WO6 and Gd2(WO4)3 with the space groups I2/a and C2/c, respectively. The phase fraction of the two monoclinic phases varies with Li+ concentrations. The Ho3+/Yb3+ co-doped phosphors show intense upconversion (UC) emission on excitation with 976 nm. Addition of Li+ ion enhances the UC emission intensity of Ho3+/Yb3+ co-doped phosphors significantly. The mechanisms involved in UC emissions have been discussed using pump power dependence analysis and energy level diagram. A hysteresis loop has been observed for Ho3+/Yb3+ co-doped phosphors in increasing and decreasing pump power versus emission intensity curves at room temperature. The polarity of the hysteresis loop is found to be reversed on addition of Li+ in the Ho3+/Yb3+ co-doped phosphors. These phosphors can be a potential candidate for optical switching devices.
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•Ho3+/Yb3+ co-doped gadolinium tungstate phosphor have been synthesized by solid state reaction technique.•The structural analyses confirm the formation of two monoclinic crystalline phases Gd2WO6 and Gd2(WO4)3.•It show intense upconversion (UC) emission and intrinsic optical bistability on excitation with 976 nm.•The polarity of the hysteresis loop is found to be reversed on addition of Li+.