Effect of Yb3+ Concentrations on the Upconversion Luminescence Properties of ZrO2:Er3+,Yb3+ Phosphors

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ZrO2:Er3+ and ZrO2:Er3+,Yb3+ phosphors were synthesized via a solvothermal reaction method. For low concentrations of Yb3+, the crystalline structure changed from the tetragonal to monoclinic phase as sintering temperature increased. As the Yb3+ concentration increased to a value above 0.05 mol, ZrO2 phosphors displayed a very stable tetragonal phase. The green and red upconversion emissions of ZrO2:Er3+,Yb3+ phosphors were measured under the excitation with a 975 nm continuous wave diode laser, and the pump power dependence of upconversion intensity was investigated. As the Yb3+ concentration increased from 0 to 0.05 mol, the red upconversion emission intensity increased more rapidly than the green emission intensity. This is attributed to the energy transfer (\text{^{4}I_{11/2}}\rightarrow\text{^{4}I_{15/2}:^{4}I_{13/2}}\rightarrow\text{^{4}F_{9/2}}) between Er3+ ions and the energy back transfer [\text{^{4}S_{3/2}:^{4}I_{13/2}(Er^{3+})}\rightarrow\text{^{2}F_{7/2}:^{2}F_{5/2}(Yb^{3+})}] between the Er3+ and Yb3+ ions. In this case, the pump power dependence of red emission intensity changed from quadratic to linear as Yb3+ concentration increased.
2013-01-25