Preparation and properties of upconversion luminescent materials of Y ₂O ₂S:Yb, Ho

The upconversion luminescent materials of Y ₂O ₂S:Yb, Ho doped with different concentrations of Yb and Ho were prepared by a flux method. The phase composition, morphology and upconversion luminescent properties of the powders were characterized by X-ray diffraction, scanning electron microscopy and fluorescence spectroscopy, respectively. The results show that the crystal structure of Y ₂O ₂S is not changed with the doping concentration of Yb and Ho. The particle shape is regular with the most of polyhedron, and the particle surface appears smooth. The particle size distribution is narrower. Y ₂O ₂S:Yb, Ho exhibits a green upconversion fluorescence under the excitation of 980nm. The optimum doping concentration of Yb and Ho is 8% (in mole) and 2% (in mole), respectively. The intensity of different emission is affected by the doping concentration of Yb and Ho. The energy transfer and cross relaxation behaviors occur between the activate ions of Ho ³⁺, causing the concentration quenching. For sensitization ion of Yb ³⁺, the excess Yb ³⁺ ions absorb energy, which is released as heat, resulting in the impurity quenching.