Yb³⁺/Li⁺ Enhanced Up-conversion Emission In SrWO₄:Er³⁺ Nanocrystalline Phosphor

Up-conversion luminescent material doped with rare earths has many advantages and a good application value,which has wide application field,but up-conversion luminescent material doped with rare earths have a relatively low emission intensity.So this article hope from the doping other rare earth ions to enhance its emission intensity.In this paper,on the basis of SrWO4:Er3+ doped different concentrations of Yb3+and Li+.Research on the Yb3+ and Li+ for Er3+ up-conversion function and the luminescent properties. The main contents and the important results are as following:1. The nanocrystalline SrWO4 doped by Er3+, Er3+-Yb3+, Er3+-Yb3+-Li+ are prepared by co-precipitation method in this paper.Crystal structure of power samples are examined by XRD. Their structure and pdf SrWO4 card standard structure(08-0490) are basically the same.This implying that the charge difference induced by Li+ ions and trivalent ions(Er3+, Yb3+) doped into the site of bivalent host ions(Sr2+) did not affect the phase structure of the SrWO4. And observe the lattice constant of the sample of rare earth ions doped single, co-doped,three-doped.2. For Er3+ single-doped SrWO4 experimental samples. Mainly observations the Er3+ the room temperature down-conversion emission and up-conversion emission Studied the relationship between Er3+ concentration of rare earth ions and down-conversion emission.The experimental result indicates that with the increase of doping concentration caused the Er3+ concentration quenching phenomenon, its optimum doping concentration is 8%. Under the 378 nm excitation,from the emission spectrum of SrWO4:Er3+ only observed blue and green emission band, red light was not observed..3. For Er3+-Yb3+ co-doped SrWO4 experimental samples. Research on the Yb3+ for Er3+ up-conversion function.Under the 976 nm laser excitation, observing the up-conversion emission of Er3+, we found that the Yb3+ can promote the up-conversion emission of Er3+.When the concentration of Er3+ is 8%,the optimum concentration for the luminescence of Yb3+ is 20 %,and we also found that the green and red up-conversion emission of 8%Er3+-8%Yb3+ co-doped SrWO4 was composed of the two-photon process. And in dealing with the experimental data, we fond an interesting phenomenon is that the up-conversion emission intensity ratio of 2H11/2-4I15/2 transition to 4S3/2-4I15/2 transition from SrWO4:Er3+-Yb3+ was increased with the increase in Yb3+ concentration. The reasonable explanation for this was discussed.4. For Er3+-Yb3+-Li+ co-doped SrWO4 experimental samples. Research on the various of Li+ for Er3+-Yb3+ up-conversion function and the luminescent properties.We determined up-conversion emission at room temperature We found that the effect of the doped concentration of Li+ on the fluorescence emission intensity shows that the optimum concentration for the luminescence of Li+ is 12.8 %. The reasonable explanation for this was discussed.