论文标题
欧盟掺杂的Sral $ _2 $ o $ _4 $中的缺陷和持续发光
Defects and persistent luminescence in Eu-doped SrAl$_2$O$_4$
论文作者
论文摘要
我们使用混合密度功能性缺陷计算研究了Sral $ _2 $ o $ _4 $中的本地点缺陷和稀土（CO）掺杂剂。在SR晶格部位发现Europium（EU）和dysprosium（DY）是混合价，并且在能量上最有利。但是，与欧盟不同的是，欧盟$^{2+} $和eu $^{3+} $可以在合成中实现，Dy主要是稳定的，因为DY $^{3+} $，而Divalent dy $^{2+} $只能在受照射下才能光生成。基于对EU相关的带fefect（包括电荷转移）和相互配置的$ 5D $ - $ 4F $ - 4F $光学过渡，我们为Eu $ $^{2+} $ $ _2 $ o $ o _2 $ _4 $ _4的特征性宽蓝色（445 nm）和绿色（445 nm）和绿色（520 nm）发射率$ \ rightArrow $ 4F^7 $在欧盟$^{2+} $中分别在SR1和SR2站点上。锶间质（与通常认为的相比）和dy $ _ {\ rm sr} $可以作为室温持续发光的有效电子陷阱。这项工作要求重新评估某些假设，这些假设是针对以前提出的所有机制所提出的特定载体捕获中心，该中心是为EU-和（EU，DY）中持续发光的持续发光所提出的。它也是理解和设计稀土掺杂磷光器的方法学模板。
We investigate native point defects and rare-earth (co)dopants in SrAl$_2$O$_4$ using hybrid density-functional defect calculations. Europium (Eu) and dysprosium (Dy) are found to be mixed valence and energetically most favorable at the Sr lattice sites. However, unlike Eu where both Eu$^{2+}$ and Eu$^{3+}$ can be realized in synthesis, Dy is stable predominantly as Dy$^{3+}$, and the divalent Dy$^{2+}$ may only be photogenerated under irradiation. On the basis of an analysis of Eu-related band-defect (including charge-transfer) and interconfigurational $5d$-$4f$ optical transitions, we assign the characteristic broad blue (445 nm) and green (520 nm) emission bands in Eu$^{2+}$-doped SrAl$_2$O$_4$ to the $4f^65d^1$ $\rightarrow$ $4f^7$ transition in Eu$^{2+}$ incorporated at the Sr1 and Sr2 sites, respectively. Strontium interstitials (not oxygen vacancies, in contrast to what is commonly believed) and Dy$_{\rm Sr}$ can act as efficient electron traps for room-temperature persistent luminescence. This work calls for a re-assessment of certain assumptions regarding specific carrier trapping centers made in all mechanisms previously proposed for the persistent luminescence in Eu- and (Eu,Dy)-doped SrAl$_2$O$_4$. It also serves as a methodological template for the understanding and design of rare-earth doped phosphors.
