掺杂离子再分布调控Whitlockite型荧光粉发光性质的研究

Tuning the luminescence properties of phosphor has always been a hot research topic in the field of inorganic luminescent materials. However, the current regulation strategies are mostly the fine-tuning of the local environment of luminescence center, and thus the tuning of luminescent spectrum is limited. In order to tune the luminescence of phosphor in a large scope, we put forward in this project redistribution of dopant ions as a new regulation strategy. The main idea is to choose β-Ca3(PO4)2 of five different cation sites as a model system. Substitution of Ca2+ with cations of different valence, size and concentration to drive the redistribution of Ce3+/Eu2+/Mn2+ ions on the host lattice may achieve the purpose of regulating the luminescent properties. The main contents of this project are as follows: (1) Synthesis and characterization of Whitlockite-type phosphors with host cations replacement; (2) Mechanism of tuning luminescence through the redistribution of dopant ions; (3) Energy transfer and device performance. On the basis of these studies, it is expected to obtain an in-depth understanding of the relationships between structure, composition and luminescence properties of Whitlockite-type phosphors, to obtain information on new mechanisms of tuning the luminescence of phosphors with multisites and the design principle of relevant materials, and to provide a basis and reference for development of new solid-state lighting phosphors.

荧光粉发光性质的调控一直是无机发光材料领域的重要科技问题。目前，调控发光的策略主要针对发光中心所处的局部环境，发光性质的调控幅度受限。为了大波长范围调控Whitlockite型荧光粉的发光性质，本课题提出掺杂离子再分布的新策略。主要思路是，选择具有五个不同格位的β-Ca3(PO4)2作为模型体系，通过不同价态、尺寸及浓度的阳离子取代Ca2+，驱动Ce3+/Eu2+/Mn2+在晶格中重新分布，达到大波长范围调控其发光性质的目的。主要研究内容如下：（1）基质阳离子取代的Whitlockite型荧光粉的合成与表征；（2）掺杂离子再分布调控发光性质的机理；（3）能量传递与器件性能。基于对这些内容的研究，有望深入理解Whitlockite型荧光粉结构、组分与发光性质的关系，探索出多格位荧光粉实现发光性质调控的新机制及相关材料的设计原则，为发展新型固态照明用荧光粉提供依据和参考。

为大波长范围调控磷钙矿型荧光粉的发光性质，本课题提出了掺杂离子再分布新策略。首先，深入理解了磷钙矿型荧光粉的发光性质与格位环境的关系。利用同价态的Sr2+和高价态的R3+（R = Gd，La，Y）取代Ca2+，研究了β-Ca3-xSrx(PO4)2:Eu2+和β-Ca3-3y/7R2y/7(PO4)2:Eu2+固溶体的发光性质与格位环境的关系。研究发现，420 nm的发射峰归属为最大的M(4)格位上的Eu2+，480 nm 的发射峰归属于M(3)格位上的Eu2+，波长更长的发射峰归属于M(2)和M(1)格位上的Eu2+。Eu2+不会占据M(5)位置。其次，揭示了磷钙矿型荧光粉发光性质的调控机制。在β-Ca3(PO4)2:Eu2+荧光粉的基质结构中，Sr2+取代引起的格位膨胀效应和R3+取代引起的格位排空效应导致的发光中心的迁移（再分布）。在β-Ca2.7Sr0.3(PO4)2:Eu2+,Mn2+中设计并实现了Eu2+-Mn2+双能量传递效应。在Ca9Y(PO4)7: Eu2+-Tb3+中，我们研究了Eu2+-Tb3+的能量传递机制。第三，提出了一种新的调控多格位荧光粉发光性质的新策略—阳离子空位修复。基于对Sr9Mg1.5-0.5xKx(PO4)7: Eu2+研究，通过引入K+修复阳离子空位，Sr9Mg1.5(PO4)7: Eu2+橘黄色发光增强了2.5倍，内外量子效率分别提升了50.5% 和 55.4%。此外，还研究了Mn4+激活的红色氟化物材料的合成、形貌调控与发光性质。.本项目的执行期间，培养了10为硕士研究生，其中3人硕士毕业，一人攻读了博士学位。共发表SCI学术论文14篇，申请美国专利2项。