绿色长余辉材料MgAl_2O_4∶Mn~(2+)的合成及其发光特性

采用高温固相法在1350℃下合成了Mn2+掺杂的MgAl2O4发光材料,利用X射线衍射对所合成样品的结构进行了表征。用209nm的紫外灯照射样品后,观察到来自Mn2+的4T1-6A1跃迁的绿色长余辉发光。发光的激发光谱表明:Mn2+-3d组态内存在一系列强的激发峰,分别在279,361,386,427,451nm,同时还有209nm处的Mn-O电荷迁移带,激发该吸收带会产生很强的绿色余辉。测量了余辉的衰减曲线及热释光谱,分析了Mn2+掺杂浓度对样品余辉性质的影响,给出了余辉产生的可能模型。

Synthesis and Luminescent Properties of Green Long-lasting Phosphorescent Materials MgAl2O4: Mn2+

Green long persistent phosphors of MgAl2O4 ∶ Mn2+ were synthesized at high temperature under weak reductive atmosphere. The XRD pattern of the sample shown that the product is the simple MgAl2O4 phase. Photoluminescence (PL) excitation and emission, long-lasting phosphorescent (LLP) emission, decay curves, and thermostimulated-luminescence (TSL) spectra were used to characterize the powder phosphor. The sample emits green LLP emission at about 520 nm when excited by 209 nm. There are two ways of excitation energy: (1)Mn2+ ions is excited directly under UV excitation between 279 nm and 451 nm, resulting in green photoluminescence; (2)For 209 nm excitation, Mn2+ ionscharge transfer transition exists, so the electrons from the Mn2+ ground state 6A1 are excited to the conduction band (CB). On one hand, the electrons in the CB can relax to the excited states of Mn2+ through nonradiative processes, and then is green emission followed. On the other hand, some of the electrons in the CB can also be trapped in the electron traps, and then released at high temperature, then turned to the excited states of Mn2+ through nonradiative processes, leading to the phenomenon of green LLP of Mn2+. The possible mechanism for this phenomenon of green LLP of MgAl2O4 ∶ Mn2+ is also investigated based on the experimental results.