Miranda de Carvalho José, Van der Heggen David, Martin Lisa I D J, Smet Philippe F
Lumilab, Department of Solid-State Sciences, Ghent University, Krijgslaan 281, S1, 9000 Gent, Belgium.
Dalton Trans. 2020 Apr 7;49(14):4518-4527. doi: 10.1039/d0dt00416b.
The performance of impurity doped luminescent materials, or phosphors, depends on the composition and crystallinity of the host compound, as well as on the distribution and valence state of the dopant ions. This is particularly true for persistent phosphors, where both luminescence centers and charge trapping defects are required. Here we show that splitting the synthesis procedure in two separate steps offers a simple way to obtain efficient persistent phosphors which are superior to phosphors prepared via a conventional solid state synthesis using a single step. The storage capacity of the persistent phosphor benefits from using a microwave assisted solid state synthesis (MASS) to achieve superior compositional homogeneity, followed by a short heat treatment in a reducing atmosphere to reduce the activators. In this work, the approach is demonstrated for the efficient blue-emitting Eu2+,Dy3+ co-doped Sr2MgSi2O7 persistent phosphor. The enhanced ionic diffusion during the MASS not only improves the homogeneity and dopant distribution, but also allows the phosphor to be obtained in considerably shorter times (ca. 25 minutes). The storage capacity of the as-obtained phosphors prepared by MASS is slightly higher than those obtained by the conventional solid-state method. Cathodoluminescence (CL) measurements evidenced however the existence of a large fraction of unreduced europium activators. Using a short reducing step at 900 °C, the Eu3+ emission was almost fully suppressed in CL and as a consequence, the storage capacity of the MASS-obtained material showed a ten fold increase, confirming the benefit of decoupling compositional homogeneity and the dopant reduction step for phosphor synthesis.
杂质掺杂发光材料（即磷光体）的性能取决于主体化合物的组成和结晶度，以及掺杂离子的分布和价态。对于长余辉磷光体来说尤其如此，因为其既需要发光中心，也需要电荷俘获缺陷。在此我们表明，将合成过程分为两个独立步骤提供了一种简单方法来获得高效的长余辉磷光体，这些磷光体优于通过传统单步固态合成法制备的磷光体。长余辉磷光体的存储容量得益于使用微波辅助固态合成（MASS）来实现卓越的成分均匀性，随后在还原气氛中进行短时间热处理以还原激活剂。在这项工作中，该方法被用于高效蓝光发射的Eu2+、Dy3+共掺杂的Sr2MgSi2O7长余辉磷光体。MASS过程中增强的离子扩散不仅改善了均匀性和掺杂剂分布，还使磷光体能够在更短的时间内（约25分钟）获得。通过MASS制备的所得磷光体的存储容量略高于通过传统固态方法获得的磷光体。然而，阴极发光（CL）测量证明存在很大一部分未还原的铕激活剂。在900°C下进行短时间还原步骤后，CL中Eu3+发射几乎完全被抑制，因此，MASS获得的材料的存储容量增加了十倍，证实了将成分均匀性和掺杂剂还原步骤解耦对磷光体合成的益处。
