Upconversion Luminescence Properties Of Rare Earth Doped Glass - Ceramics Based On NaYF4 + Nanocrystals

The lanthanide-doped micro-crystal materials have attracted considerable attentions in the field of optical fibers, solid laser, three-dimensional display and W-LED illumination etc. Fluoride glasses are ideal for rare-earth doped substrate, on account of its high transparency, rare earth ions solubility and the low phonon energy. However, the prices of the fluoride glass are expensive and it is toxic, susceptible to corrosion and of poor stability. It should be prepared under a dry condition with plenty of oxygen. This has led to the reliability of the equipment, hindering the application of communications engineering. Lanthanide-doped oxides possess excellent chemical and mechanical stability, but it has high photon energy, resulting in poor up-conversion emission. Fluorine oxides taking into account of the high mechanical strength and good conversion efficiency of the oxides, become a hot research and get some interesting results.In this paper, mainly for rare earth ions Er³⁺Yb³⁺ and Tb³⁺/Yb³⁺ glass-ceramic luminescent material doped by regulation of the glass structure to achieve the regulation of rare earth ions luminescence properties, and mechanism of action of various structures control methods were studied.（1） Different change the glass network modified form of alkali metal oxides R2O （R= Li, Na, K） species, to influence the crystallization behavior of the glass-ceramic, glass change how closely each network structure such that heat treatment samples obtained in different sizes NaYF₄ grains by EDS spectrum test that, with different grain sizes in Er³⁺/Yb³⁺ion concentration is proportional with the size, control Er³⁺ crystal cross-relaxation phenomenon to regulate the conversion of light emission hair color, light color and intensity makes the conversion reaches controllable adjustment.（2） By changing the ratio of the glass network structure modified form MgO and Na2O, regulating the crystallization behavior of glass-ceramics, the degree of difficulty of regulating the grain grown in the glass matrix so that the grain size obtained under well controlled control NaYF₄ precipitated grains grain spacing, so that the distance between the grains Er³⁺ ions has been effectively controlled, and change its upconversion luminescence properties. This material is expected to be used as color-tunable visible laser material or display material, and may also provide a new direction for the application of white LED crystal glass.（3） By changing the ratio of the glass network structure and intermediate ZnO modified form Na20, and significantly improved the crystallization temperature of the glass, while increasing the link level network structure of the glass, so that the resulting heat-treated from opposite cubic crystals NaYF₄ hexagonal phase transition. Since the hexagonal lattice symmetry NaYF₄ than cubic symmetry NaYF₄ low, more conducive to Tb³⁺/Yb³⁺ co-doped upconversion luminescence efficiency, so the transition NaYF₄ crystalline structure enhances the conversion luminescence intensity.（4） NaYF₄ grains incorporated in a smaller radius of Li+ ions, were interstitial solid solution in which grains vary cubic lattice symmetry NaYF₄ of Tb³⁺ at a lower crystal symmetry in favor of the electron cloud the polarization enhancement layer 4f electron transitions but upconversion luminescence intensity increases. This provides an effective method for improving the conversion efficiency of the luminescent material.