Abstract
Ba2YF7:xYb3+,0.02Er3+ nanocrystals with different Yb3+ concentration (x=0.2, 0.4, 0.6, 0.8, 0.98) were synthesized via a solvothermal method. Their X-ray diffraction patterns reveal that all the samples are cubic phase without phase change at arbitrary Yb3+ concentration. Upon excitation of 980nm laser, these nanocrystals display upconversion emission in the green and red spectral regions. The relative emission intensity at these two regions can be tuned by Yb3+ concentration. To investigate the effect of Yb3+ ion, the decay times of 650nm emission were measured and analyzed. Ba2YF7:0.6Yb3+,0.02Er3+ nanocrystals have the longest lifetime and highest emission intensity among all the samples. We concluded the lifetime of 4F9/2 level has an effect on its own population and intensity ratio of red and green emission. Our results show Yb3+ ion can tune the upconversion emission and improve upconverison emission intensity.
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