| Eu as an activator ion doped in the matrix, enables the system to produce a luminous effect, so Eu ions are doped a large number of inorganic luminescent materials. The main valences of Eu are+2and+3, respectively. According to Hund’s rule, an ion is relatively stable when all its orbitals are completely empty, full or half-full state, therefore, Eu3+can be reduced to the Eu2+under specific conditions. However, light emission characteristic of Eu3+is different from Eu2+. Eu3+spectrum contains a series of sharp peaks, and its emission characteristic peaks at about592,616nm. The emission spectrum of Eu2+exhibits broadened bands. A series phosphors samples of Sr3MgEuSi2O8:Ln3+(Ln:Dy, Er, Ho)and Zn3(BO3)2: Eu3+, A+(A=Li, Na, K) were synthesized by high temperature solid state reaction. The crystal structure were characterized by X-ray diffraction (XRD), and the photoluminescence spectra, the decay curve and thermoluminescence(TL) spectra were measured by fluorescence spectrometer, single-photo counter and micro-computer thermoluminescence dosimeter, respectively. The main conclusions obtained were as follows:1. Afterglow and TL properties of Eu2+in Sr3MgSi2OsThe luminescent properties of Sr3MgEuSi2O8phosphors have been investigated with different Ln3+(Ln3+:Dy3+, Er3+, Ho3+) co-dopants. The co-dopants have no influence on both the structure of the lattice and the position of the emission peak. However, the afterglow properties of samples have been enhanced with different co-dopings. The afterglow duration of the Dy3+co-doped sample shows longer than the others. Furthermore, the co-doping samples have stronger TL intensity and therefore longer afterglow duration. At last, the self-reduction of Eu3+â†'Eu2+was observed in an silicate compound of Sr3-xMgSi2O8:xEu phosphor in air condition. This is the first time to show a blue long afterglow phosphor synthesized avoiding reducing atmosphere.2. Charge compensation for the luminescence of Eu3+in Zn3(BO3)2For the system (Eu3+doped Zm3(BO3)2), the results of XRD analysis show that all samples exhibit Zn3(BO3)2crystalline phase. The samples co-doped with alkali metal ions have better crystallinity compared with the un-compensated ones. The strongest excitation peak locates at393nm which is good agreement with the emission used InGaN-based UV LEDs. The different charge compensation approaches have no influence on the shape and position of the emission and excitation spectra. However, the luminescent intensity of samples has been obviously enhanced with different alkali metal ions co-doping. Li+, Na+or K+can be substituted Zn2+. The introduction of Li+is the optimal followed by Na+, K+and self-compensated. Compared with the uncompensated samples, they can enhance the red emission intensity of Eu3+by3.3,2.5,2.4and2.0times, respectively. Accordingly, the charge compensation is an effective means of enhancing the intensity of the light emitting center. It is not enough to only rely on charge compensation. Thus, the volume compensation and the equilibrium of mole number can be taken into consideration by charge compensated (CC) approaches.In this paper, the investigation on the properties of two light-emitting materials doped europium ions has been carried out. And we hope that this will provide useful information for improving the performance of the light-emitting materials. |
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