铬掺杂持久发光AB $_2$ O $_4$尖晶石中Cr $^{3+}$周围的有序和无序
Order and disorder around Cr$^{3+}$ in chromium doped persistent luminescence AB$_2$O$_4$ spinels
摘要：
利用X射线吸收近边结构（XANES）光谱技术研究了Cr $^{3+}$掺杂AB $_2$ O $_4$尖晶石（A = Zn，Mg，B = Ga，Al）在低光子能量下可见光激发下的持续发光的充放电过程.对Cr $^{3+}$复合中心附近不同近邻环境的Cr K边XANES谱进行了模拟，并与实验曲线进行了比较。在Cr $^{3+}$：ZnGa $_2$ O $_4$化合物中，Cr $^{3+}$局部结构主要对应于正常尖晶石的结构（$\sim$ 70\%），而其余部分包括由阳离子位点反转产生的扭曲八面体环境和铬簇集的贡献。这种局部结构在Cr $^{3+}$：MgGa $_2$ O $_4$和Cr $^{3+}$：ZnAl $_2$ O $_4$中是强烈不同的，其中，对于这两种情况，铬簇合代表主要贡献。团簇中Cr的含量与发光强度之间的强相关性使我们推断Cr团簇的存在是导致Cr $^{3+}$掺杂AB $_2$ O $_4$尖晶石中可见光诱导发光强度降低的原因。
英文摘要：
X-ray absorption near edge structure (XANES) spectroscopy technique is used to better understand the charging and decharging processes of the persistent luminescence in the Cr$^{3+}$ doped AB$_2$O$_4$ spinels (A = Zn, Mg and B = Ga and Al) with low photon energy excitation by visible light. Cr K edge XANES spectra have been simulated for different near neighbour environments around the Cr$^{3+}$ recombination centres and compared with the experimental curve. In Cr$^{3+}$:ZnGa$_2$O$_4$ compound, the Cr$^{3+}$ local structure corresponds mostly to that of a normal spinel ($\sim$70\%), while the rest comprises of distorted octahedral environment arising from cationic site inversion and a contribution from chromium clustering. This local structure is strongly different in Cr$^{3+}$:MgGa$_2$O$_4$ and Cr$^{3+}$:ZnAl$_2$O$_4$ where, for both cases, chromium clustering represents the main contribution. The strong correlation between the intensity of persistent luminescence and \% of Cr in clusters leads us to infer that presence of Cr clusters is responsible for decrease of the intensity of the visible light induced persistent luminescence in the Cr$^{3+}$ doped AB$_2$O$_4$ spinels.
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