Tuning emission color and improving the warm-white persistent luminescence of phosphor BaLu 2 Al 2 Ga 2 SiO 12 :Pr 3+ via Zn 2+ co-doping

In this article, we synthesized a series of new warm-white emitting persistent luminescent phosphors by co-doping Zn 2+ into Pr 3+ activated BaLu 2 Al 2 Ga 2 SiO 12 , and systematically investigated the effect of Zn 2+ 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 3 P 0 and 1 D 2 multiplet electron transitions at the 4f level of Pr 3+ . The luminescence properties of the Ba 1− x Zn x Lu 2 Al 2 Ga 2 SiO 12 :Pr 3+ phosphors can be modified by changing the content of Ba/Zn in the host, which affects the non-radiative energy flow between 5d 1 – 3 P 0 – 1 D 2 levels and resultantly enhances the intensity of the 4f → 4f transition. Compared with the undoped sample, Zn 2+ 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, Zn 2+ 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 Zn 2+ concentration. Besides, the Zn 2+ 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 BaLu 2 Al 2 Ga 2 SiO 12 :Pr 3+ ,Zn 2+ phosphor.