自还原合成白光LED用Eu2+-Eu3+掺杂铝酸盐和硅酸盐发光材料的自还原机理及发光特性研究

In the present project, the Eu2+-Eu3+doped aluminates and silicate phosphor materials of single host for white light LED application will be designed, researched and prepared, which is based on the self-reduction theory of the rare earth in air condition at high temperature. The broad band emission ranging from blue to green light can be obtained from the bivalent europium ions. The same time, the red light is from the trivalent europium ions. So white light emission with high efficiency can be achieved through controlling the relative proportion of divalent europium ions to trivalent ones by the modulated reduction. In the present project, the aluminates and silicate single host with white light emission prepared at atmosphere , will be successfully obtained by controlling the composition of the host, the doping variety （charge compensation， modulated structure， co-doping of the activators with europium ion and so on）, the reaction preparation condition and engineering to achieve the reduction of trivalent europium ions to divalent ions. Moreover, the bivalent europium ions have broad band absorption itself at near ultraviolet range which match with the commercial LED chips, and can transfer to other luminescent centers, effectively. It implies that it can be effectively cooperated with the near ultraviolet LED chips, to obtain high efficiency and high color index emission. To further study and clarify the mechanisms of the self-reduction and the physical mechanism of the luminescence, the some modern spectrum methods (excitation spectra, emission spectra, high resolution spectra, luminescent dynamitic, etc) are used to study the luminescent characteristics and self-reduction mechanisms, combining the structure theory of the materials. The project is the theory and practice purposes for developing advanced luminescent materials for white light LED and device.

本研究基于稀土离子的高温自还原原理设计、开发和制备Eu2+-Eu3+掺杂铝酸盐和硅酸盐单一基质白光LED用荧光材料。二价铕离子存在蓝光到绿光发射，三价铕离子存在红光特征发射，通过调控自还原控制其相对比例，实现单一基质高效白光发射。采用固相法在空气气氛中自还原制备铕离子掺杂铝酸盐和硅酸盐荧光材料，控制基质组成、掺杂方式（电荷补偿掺杂、结构调制掺杂、激活剂共掺杂等）、制备条件和工艺等手段实现三价铕离子还原为二价铕离子，调制其发光特性实现高效白光发射。二价铕离子在近紫外区域存在有效的宽带吸收，与商业LED近紫外芯片匹配，可通过能量传递给其它发光中心，获得高效和高显色指数的白光发射。利用现代光谱手段（激发、发射、高分辨光谱、荧光动力学等），系统研究材料的发光特性，结合材料的结构化学理论，深刻理解和揭示自还原机理和发光的物理机制。该研究对于开发新型白光LED用荧光材料和器件具有重要的理论和实际意义。

在过去的4年中，在基金委的资助下，项目顺利开展，针对铝酸盐、硅酸盐和磷酸盐以及氧化物复合材料体系的组成、结构和发光特性展开系统的研究，取得成果主要有：（1）采用高温固相法制备了Eu离子掺杂的硅酸盐和铝酸盐体系荧光材料，研究组成、掺杂离子浓度、添加网络改变体等对于基质结构和发光特性的影响，特别是自还原过程以及由此导致的Eu2+和Eu3+发光强度的变化。结果表明改变硅酸盐/铝酸盐中的硅/铝比例，硅酸盐中添加氧化锆和氧化锡极大改变了基质中Eu2+和Eu3+相对发光强度，并获得最优化组成，实现单一基质的白光发射（2 ）采用高温固相法制备了Eu2+和Eu3+离子掺杂的磷酸盐荧光材料，发现一些单一正磷酸盐基质中没有观察到二价铕离子的发射，而在其中添加硼以及复合磷酸盐或者多磷酸盐中，例如Mg21Ca4Na4(PO4)18、Mg21Ca4Na4(PO4)18、Sr2P2O7基质中同时观察到Eu2+和Eu3+发射，表明三价铕离子通过自还原获得二价铕离子，并且实现高效的单一基质白光发射（3）高温固相法制备了Al2O3-SiO2/MgO的ZrO2-MgO/SiO2/Al2O3体系的复合材料，在单一氧化物体系中，没有观察到二价铕离子的发射，但是在氧化物复合材料中，观察到强的Eu2+和Eu3+的发射，系统研究了组成和结构对发光特性以及自还原过程的影响规律，并且获得单一基质的高效白光发射。