采用改进的两步高温固相熔融法制备了Yb3+、Eu3+、La3+共掺杂CaF2的上转换荧光粉。基于荧光猝灭原理, 通过改变La3+掺杂浓度来调节CaF2∶Yb3+/Eu3+材料的发光性能, 并在980 nm近红外光激发下, 获得了该材料的白色上转换发光(UCL)。在该发光体系中, Yb3+不仅起到了敏化Eu3+的作用, 同时, Yb3+二聚体(Yb3+-dimer)自身合作发出波长范围480~540 nm的绿色荧光。而白光三基色中的绿光正是来自Yb3+二聚体的合作发光。Eu3+则作为激活剂, 同时发出红色和蓝色荧光。荧光寿命测试结果表明Yb3+-dimer与Eu3+之间存在有效的能量传递。值得注意的是, 在980 nm 激光激发下, 1% La3+掺杂的样品表现出最佳的红、绿、蓝三基色光比列, 实现了材料的上转换白光发射, 其色度坐标为(0.311,0.340)。

Yb3+, Eu3+, La3+ co-doped CaF2 upconversion phosphors were synthesized by a modified two-step high temperature solid phase method. On the basis of fluorescence quenching theory, the luminescence properties of CaF2∶Yb3+/Eu3+ materials were adjusted by changing the doping concentrations of La3+, and the white upconversion luminescence (UCL) of these materials was obtained under a 980 nm laser. In this UCL system, Yb3+ not only sensitizes Eu3+ but also cooperates with neighboring Yb3+ to emit green luminescence in the wavelength range of 480-540 nm. This green luminescence just happens to be an important component of white light. In addition, Eu3+ ions act as activators and emit both red and blue luminescence, providing two other elements in the tri-color light. Fluorescence dynamical analysis indicates that an efficient energy transfer exists between the Yb3+-dimers and Eu3+ ions. It is remarkable that the white UCL can be achieved from the 1% La3+-doped sample, and the color coordinate is (0.311, 0.340).