Eu<sup>2+</sup>掺杂CaAlSiN<sub>3</sub>基氮化物红色荧光粉及其发光性能研究

doi:10.3964/j.issn.1000-0593(2020)01-0059-06

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摘要：白光LED作为新一代高效、环保型照明光源，被给予了极高的厚望。目前商业中白光LED主要采用蓝色LED芯片激发黄色YAG荧光粉的方式来实现白光，发光效率能达到理想值，但存在红色光谱区域缺失的问题，造成关键性指标显色指数偏低，限制了白光LED在橱窗照明、医疗照明和投影显示等高品质需求领域的应用。而目前研究较多有关红色荧光粉的光效与稳定性，对红色氮化物荧光粉的宽光谱设计研究尚有待深入探索。采用高温固相法成功制备出了高效宽光谱红色Ca_0.992AlSiN₃∶0.008Eu²⁺荧光粉，通过X射线衍射仪(XRD)和荧光光谱仪(PL)等测试技术对荧光粉样品的结晶度和发光性能进行了表征分析；基于第一性原理研究了CaAlSiN₃∶Eu²⁺荧光粉的晶体结构和能带结构，研究了Eu²⁺掺杂CaAlSiN₃发光过程中的能量跃迁机理，从其微观性质方面分析探讨了荧光粉的光谱性能；基于蒙特卡罗理论和遗传算法建立了白光封装模型，并结合CaAlSiN₃∶Eu²⁺进行了白光LED应用封装和测试，研究了CaAlSiN₃∶Eu²⁺荧光粉的封装样品的光色特性。研究结果表明，利用高温气压炉合成Ca_0.992AlSiN₃∶0.008Eu²⁺材料具有较高的结晶度，且微量的稀土元素Eu掺杂不会破坏其晶体结构，仍具有较好的稳定结构；通过PL光谱测试发现其具有极宽的激发光谱（200～600 nm），能被蓝光或者紫外LED芯片有效激发，当在450 nm波长激发下，荧光粉发出峰值为650 nm的发射光谱，光谱半高宽为91.4 nm，通过晶体的能带分布可知其发射光谱为5条高斯光谱曲线，归结于Eu²⁺ 的5d能级向4f能级跃迁，Ca_{0.937 5}AlSiN₃∶0.062 5Eu²⁺荧光粉的能量带隙为3.14 eV的间接带隙，主要是由Ca-3p，Eu-3d，N-2p，Al-3p，Si-3p电子态决定，使得材料发出红色光谱；通过建立白光光谱模型指导实现了白光LED应用封装，采用蓝光LED芯片与Ca_0.992AlSiN₃∶0.008Eu²⁺红色荧光粉、β-sialon绿色荧光粉进行组合封装，光谱测试结果与白光封装模型模拟值（R_a=93.93，R₉=72.77，T_c=3 400 K）的趋势接近，且获得了高效高显色性的白光LED（η=101 lm·W^-1，R_a=92.1，R₉=74.9，T_c=3 464 K），Ca_0.992AlSiN₃∶0.008Eu²⁺所提供的红光光谱能够有效地提高白光LED的显色指数，同时在LED的发光效率、色温和物理化学稳定性等方面具有极高的价值，是一种很有应用前途的高品质照明白光LED用红色荧光粉材料。

关键词：氮化物荧光粉；稀土掺杂；晶体结构；发光性能；白光LED

Abstract：White light-emitting diodes (wLEDs) are one of most efficient and environmentally friendly lighting technologies, which are known as indispensable solid-state light sources. At present, the commercial way to produce wLEDs is combining a blue chip with yellow phosphor material as YAG∶Ce³⁺. The luminous efficacy of the wLEDs could reach the ideal value, but the color rendering is poor, which could be ascribed to the lack of red component in the emission spectrum. Thus, the development of wLEDs is limited in the application of high-quality general lighting, such as showcase lighting, medical illumination and projection display. A promising deep red phosphor, Eu²⁺ doped CaAlSiN₃ (CASN) was prepared by high temperature solid reaction in a gas pressure sintering furnace. In this work, luminescent properties, crystal structure of the CASN were investigated via X-ray diffraction (XRD) and photoluminescence spectra (PL), by applying the structure and bandgap engineering strategies, we have revealed the essential energy transfer mechanism of its luminescence phenomenon. The XRD results indicate that the sample is well-crystallized in the combustion procedure, and its crystal structure has not changed when doped with low concentrations of rare-earth ions. Ca_0.992AlSiN₃∶0.008Eu²⁺ phosphors could be effectively excited by a broad emission spectrum extending from 200 to 600 nm, and this broad excitation band could be deconvoluted into five sub-bands by Gaussian fitting. A substantial red spectra is centered at 650 nm under the 450 nm excitation, with a wide broad full width at half maximum (FWHM) of the emission spectrum(91.4 nm), due to the electron transfer of Eu²⁺ from 5d to 4f. The band structure calculation shows that Ca_{0.937 5}AlSiN₃∶0.062 5Eu²⁺ has an indirect band gap with an energy gap of about 3.14 eV, with the atomic projected Ca-3p, Eu-3d, N-2p, Al-3p, Si-3p states. An optimal spectral model was designed to guide packaging of the phosphor-converted wLEDs, and the influence of the various combination of Ca_0.992AlSiN₃∶0.008Eu²⁺ phosphors was studied with the wLED packaging. A super wLED was attained by combining red Ca_0.992AlSiN₃∶0.008Eu²⁺ phosphor and green β-sialon phosphor with a blue LED chip, showing a high color rendering index of 92.1, a high luminous efficacy of 101 lm·W^-1, and a warm color temperature of 3 464 K. The phosphor of Ca_0.992AlSiN₃∶0.008Eu²⁺ is effective to improve color rendering indexes for wLEDs with the contribution of its red spectral part with simultaneous spectral broadening, meanwhile it is of great value in luminous efficacy, color temperature and stability, which means that it is a promising candidate for the red phosphor material for wLEDs.

Key words：Nitride phosphor; Rare earths; Crystal structure; Luminescence properties; wLEDs

收稿日期: 2018-11-13 修订日期: 2019-03-19

中图分类号:

TQ174

基金资助: 国家重点研发计划项目（2017YFB0403100，2017YFB0403105），国家自然科学基金项目(61575182)，浙江省省杰出青年基金项目（LR19F050001），浙江省公益技术应用研究计划项目(2018C37042)资助

通讯作者: 王乐 E-mail: calla@cjlu.edu.cn

作者简介: 张宏，1989年生，中国计量大学光学与电子科技学院实验师 e-mail: zhanghong@cjlu.edu.cn

引用本文:

张宏，王乐，罗东，郑紫珊，李旸晖，潘贵明. Eu²⁺掺杂CaAlSiN₃基氮化物红色荧光粉及其发光性能研究[J]. 光谱学与光谱分析, 2020, 40(01): 59-64.
ZHANG Hong, WANG Le, LUO Dong, ZHENG Zi-shan, LI Yang-hui, PAN Gui-ming. Structural and Luminescence Properties of Eu²⁺ Doped CaAlSiN₃ Silicon Nitride Red Emitting Phosphor. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2020, 40(01): 59-64.

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https://www.gpxygpfx.com/CN/10.3964/j.issn.1000-0593(2020)01-0059-06 或 https://www.gpxygpfx.com/CN/Y2020/V40/I01/59