Tuning emission color and improving the warm-white persistent luminescence of phosphor BaLu2Al2Ga2SiO12:Pr3+via Zn2+ co-doping

Abstract

In this article, we synthesized a series of new warm-white emitting persistent luminescent phosphors by co-doping Zn²⁺ into Pr³⁺ activated BaLu₂Al₂Ga₂SiO₁₂, and systematically investigated the effect of Zn²⁺ co-doping on both their photoluminescence and persistent luminescence properties. Following the removal of UV excitation, the phosphor emits warm-white persistent luminescence consisting of greenish-blue and red emissions originating from ³P₀ and ¹D₂ multiplet electron transitions at the 4f level of Pr³⁺. The luminescence properties of the Ba_1−xZn_xLu₂Al₂Ga₂SiO₁₂:Pr³⁺ phosphors can be modified by changing the content of Ba/Zn in the host, which affects the non-radiative energy flow between 5d¹–³P₀–¹D₂ levels and resultantly enhances the intensity of the 4f → 4f transition. Compared with the undoped sample, Zn²⁺ co-doping can significantly enhance the persistent luminescence intensity of the phosphors in the range of 400–800 nm and reduce the intensity in the UV region. Meanwhile, Zn²⁺ co-doping can also change the intensity ratio between the greenish-blue and red emissions, and the persistent luminescence color can be tuned from red to warm-white with the increase of Zn²⁺ concentration. Besides, the Zn²⁺ ions entering the crystal lattice also enhance the persistent luminescence performance by modifying the defect levels in the phosphor. For the optimized phosphor, bright warm-white persistent luminescence can be observed by the naked eye in the dark after the removal of the excitation source for 4 h. Based on the experimental results, a feasible mechanism was also proposed to reveal the persistent luminescence generation process for the BaLu₂Al₂Ga₂SiO₁₂:Pr³⁺,Zn²⁺ phosphor.