基于硅基氮/氮氧化物荧光体的微结构相关荧光热淬灭机理研究

As a strategic energy conservation and environmental protection plan, white LED (WLED) for indoor-illumination has been proposed in demonstration-scale application and popularization. The phosphor conversion LED can be usually used to realize the white light emitting (pc-WLED), in which the conversion phosphors are playing an important role. However, the poor heat resistance of luminescence greatly limits the wide application of high power pc-WLED and makes it in the bottleneck of technology for indoor-illumination. Meanwhile, the impact of different crystal structure and local-structure on luminescence decay at higher temperatures has not clear in the phosphors. Moreover, controlling the luminescence thermal stability has been barely studied. Herein, several types of (oxo)nitridosilicate phosphors doped with Eu2+ ions will be synthesized and characterized by XRD, TEM, SEM, and PLE/PL measurement. The mechanism of crystal structure and local-structure, such as the phase, space configurations, luminescent sites and coordination environment, influencing on the luminescence thermal-quenching will be investigated thoroughly. Various designs towards local-structure will be carried out to control luminescence thermal stability with modulating local-structure based on one type of nitridosilicate phosphors. Combining the temperature dependent luminescence characteristics, the parameters related energy transmission, such as electron-phonon coupling strength, Stokes shift and activation energy, are calculated to indicate the relationship between local-structure factors and luminescent thermal stability complementally. These researches provide the theoretical basis and practical guidance of material selection, structure design and controllable preparation for developing novel phosphors with high luminescence thermal-quenching temperature.

室内白光LED（WLED）照明作为战略性节能环保计划，其示范应用和推广已经被提上日程。荧光转换型LED技术是WLED产生白光的主要方法（pc-WLED），其关键部分荧光粉的荧光耐热性较差严重限制大功率pc-WLED的室内照明应用。提高荧光粉的荧光热稳定性成为急需解决的关键问题。然而，与荧光粉的结构及微结构相关的热致光衰方式还不很明确，对其荧光热稳定性控制的研究还没有全面展开。本项目拟合成和表征几类不同结构及微结构的Eu2+离子激活硅基氮/氮氧化物荧光体，探讨晶相、晶体构架、发光格位性质及配位性质对荧光热淬灭的影响机制。对一类硅基氮化物进行微结构设计，实现微结构调变对荧光热稳定性的控制，计算相关电-声耦合强度、Stokes位移及活化能等能量传递参数，揭示结构微观因素与荧光热稳定性间的变化规律，为开发具有较高荧光热淬灭温度的新型荧光粉的材料选择、结构设计和可控制备提供可靠的理论依据和实践指导。

室内白光LED（WLED）照明作为战略性节能环保计划，其示范应用和推广已经被提上日程。荧光转换型LED技术是WLED产生白光的主要方法（pc-WLED），其关键部分荧光粉的荧光耐热性较差严重限制大功率pc-WLED的室内照明应用。提高荧光粉的荧光热稳定性成为急需解决的关键问题。本项目主要针对几类不同晶体结构及微结构Eu2+离子激活硅基氮/氮氧化物荧光体的温度依赖光谱特性进行研究，探讨晶体对称性、晶体组成构架、发光离子所处格位及其配位情况对荧光热稳定性的影响机制和规律。本项目的研究内容和成果有：.1. 通过对已知硅基氮/氮氧化物荧光体的结构及微结构进行深入细致分析，提出了一种比较方法。按不同晶体对称性、晶体构架、发光格位性质、配位原子数目等进行科学分类。.2. 在制备MSi2O2N2（M=Ca, Sr）: Eu2+、SrSiN2: Eu2+和SrSi5N8: Eu2+材料过程中，提出了一种新的制备方法：压片碳热还原高温固相法，该法使用便宜的原料（如碳酸锶、氧化铕），在空气中配料操作，且对硅基氮化物材料实现了常压下高温煅烧。该法使该类材料制备不再依赖特殊设备和原料（如：手套箱、热压炉、氮化物），大大降低了制备成本。而且，碳热还原替代H2气氛还原，不但降低气体成本约3倍，且工艺安全性得到提升。该法可作为一种常规方法具有重要的参考意义。.3. 揭示Eu2+离子激活硅基氮/氮氧化物荧光体晶体对称性、晶体构架、发光离子位配位数及配位原子对荧光热稳定性的影响规律。同一体系，晶体对称性高的荧光热稳定性较高；晶体构架为非金属层和碱土金属离子Sr2+层（Eu2+取代层）相间的层状结构的荧光热稳定性较高；基质具有[SiN4]四面体共边相连特点的比[SiN4]四面体是共点相连的荧光热稳定性较差；具有发光离子与O键合特点的比与N键合的荧光热稳定性较差；具有发光离子配位数多的比配位数少的荧光热稳定性较差。Stokes位移可以作为一种参数初步判断或比较材料的荧光热稳定性。此结果为开发具有较高荧光热淬灭温度的新型荧光粉的材料选择和结构设计提供可靠的理论依据。