(Eu 2+ , Dy 3+ )-co-doped strontium/calcium aluminate phosphor as one of color-tunable emission materials was synthesized via solid-state reactions at 1300 °C for 3 h. Effect of strontium/calcium ratio on the crystal structure, particle size/morphology as well as photo- and mechano-luminescent properties of the phosphors was investigated by X-ray diffraction, Rietveld method, scanning electron microscopy with energy dispersive X-ray spectroscopy, and spectrophotometry . The mechano-luminescent properties were measured by two mechanical stress instruments (i.e., impact and compression), respectively. The results reveal that a mixed phase with SrAl 2 O 4 and CaAl 2 O 4 has a monoclinic structure with a space group P2 1 for Sr x Ca 1-x Al 2 O 4 : 0.001Eu 2+ , 0.001Dy 3+ phosphor (x = 0.2–0.8), resulting in the change of crystallographic parameters due to different calcium/strontium ratios. According to the results of photo- and mechano-luminescent characterizations, SrAl 2 O 4 : 0.001Eu 2+ , 0.001Dy 3+ phosphor (x = 1.0) has a superior mechano-luminescent property rather than CaAl 2 O 4 : 0.001Eu 2+ , 0.001Dy 3+ phosphor (x = 0), although they both have photo-luminescent properties. Furthermore, the CEI diagram indicates that the emission color of the phosphor can be tuned from blue to bluish white and eventually to green, and the mechano-luminescent peak appears and becomes intense as Sr 2+ ions substitute for Ca 2+ ions in the phosphor gradually. In addition, the photo- and mechano-luminescent mechanisms of phosphor were also discussed.
Hao Song,Xiuping Wu,Yanjie Zhang,Shichang Xu,Bing Li
Deep-trap luminescent materials have attracted great attention for optical information storage applications. However, the flexible luminescence films based on red luminescence materials with temperature and infrared response are scarce. In this study, we have successfully developed various novel flexible red emitting films based on Eu 2+ /Dy 3+ co-doped Sr 2 Si 5 N 8 phosphors through screen-printing and spin-coating technologies, respectively. Interestingly, the fabricated flexible luminescence films exhibit unique temperature and infrared responsive properties for optical information storage by releasing photons in response to thermal or infrared stimulation. Notably, deep-trap red emitting Eu 2+ /Dy 3+ co-doped Sr 2 Si 5 N 8 phosphors are crucial for the optical information storage properties of the films. Two emission peaks of Sr 2 Si 5 N 8 :Dy 3+ phosphors at 476 nm and 577 nm are observed under excitation at 345 nm, corresponding to the radiative transition occurs from the 4 F 9/2 level to the 6 H 13/2 and 6 H 15/2 levels of Dy 3+ . When Dy 3+ and Eu 2+ ions are co-doped in Sr 2 Si 5 N 8 , the energy transfer from Dy 3+ to Eu 2+ in Sr 2 Si 5 N 8 matrix is found and the decay time confirms that Dy 3+ ions can be acted as deep trap centers to storage photons. For Sr 2 Si 5 N 8 :Eu 2+ ,Dy 3+ phosphors and the corresponding flexible luminescence films, the specific patterns (for example apple and note patterns) are firstly recorded under NUV or blue light excitation and then reappear through thermal stimulation or near-infrared photo-stimulation (980 nm laser). This work not only validates the feasibility of Sr 2 Si 5 N 8 :Eu 2+ ,Dy 3+ phosphors as deep-trap red emitting luminescence materials, but also suggests the applications of flexible luminescence films for optical information storage.
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