【作者】 解文杰；

【导师】 徐鑫；

【作者基本信息】 中国科学技术大学 ， 材料学， 2010， 博士

【摘要】 1996年日本日亚公司以超高亮度GaN蓝色发光二极管(light emitting diode,简称LED)为基础开发出了白光LED照明器件。白光LED相对于传统白炽灯和荧光灯具有体积小(颗粒小、易组合)、发热量低(无热辐射)、耗电少、寿命长(大于10000小时)、反应快、环保(无污染、可回收)等优点,因此在全球半导体和照明领域掀起了一股白光LED热潮。半导体材料的发光机理决定了单一LED芯片不可能发出连续光谱的白光,目前实现白光LED主要有三种方法：(1)用红绿蓝的三色LED,按照所属光的强弱排成矩阵,三种色光复合后产生白光,但是工艺和控制系统非常复杂；(2)利用蓝色LED和可被蓝光有效激发的红、绿荧光粉(或黄色荧光粉)有机组合,使用过程中LED发出蓝光激发荧光体产生红、绿(黄)光,没被吸收的蓝光和荧光体发出的红绿光混合成白光,其既避免了伤害眼睛的紫外光,又降低了能量消耗；(3)像三基色节能灯那样,利用紫外光LED和可被紫外光有效激发的红、绿、蓝三基色荧光体有机组合而产生白光,由于其具有红绿蓝三基色发光,理论上可以调配成任何色温的光源,而且其显色性更好,制备更加简单。作为白光LED不可缺少的部分,荧光粉成为白光LED发展的关键之一。传统荧光粉的基质材料主要由硫化物、铝酸盐、硅酸盐等构成。近来,国内外相继出现了以稀土掺杂硅基氮化物和氮氧化物荧光材料的报道,如Sr2Si5N8：Eu2+,Ca-α-SiAlON：Eu2+等。氮化物和氮氧化物相对于硫化物和氧化物来说,由于氮具有相对较小的电负性和较大的电子云膨胀效应,有效促进稀土离子5d能级在晶体场中的分裂,从而使5d-4f之间的能级差减小,激发-发射波长红移,与紫外或蓝光LED匹配。同时可以通过在很大范围调节氮氧比例来控制激发-发射波长,使荧光粉具有较优的可控性,提高白光LED的性能,同时氮以及氮氧化物还具有稳定的化学性质和优良的高温发光性能。本论文主要进行新型硅基氮氧化物荧光材料的探索,深入研究其制备技术、晶体结构、光转换性能以及优化调控机理,期望在深入研究其发光特性的基础上,探讨其在白光LED上的应用可行性。本文主要分为五章,第一章文献综述主要介绍了照明发展的历史,着重介绍了白光LED的应用。并对白光LED用荧光粉进行了介绍。第二章为实验部分,第三章第四章分别介绍了以M2Al2Sil0N1404和MgYSi205N为基质进行稀土掺杂所得到荧光粉的性质。第五章对前面的实验进行了总结并且展望其在白光LED中的应用。在第三章中通过高温固相反应合成Ba2Al2SiloN1404,Sr2Al2Sil0N1404和Ca2Al2SiloN1404相,并通过X射线衍射(XRD),电子扫描显微镜(SEM),对其结构和形貌进行分析,基于XRD数据,利用Unitcell软件计算晶格参数,并通过激发-发射光谱研究了相关荧光粉的光转换性能和优化调节机理。结果发现：1、在1atm的N2气氛保护,1600℃的煅烧温度下可以形成Ba2Al2SiloN1404单相,Ba2Al2Sil0N1404：Eu2+的激发波段位于300nm,半高宽范围为270nm-350nm,发射光谱范围为476nm-527nm。2、在1atm的N2气氛保护下进行煅烧无法得到纯Sr2Al2Sil0N1404相,但当以非常少量的Ba作为稳定剂时,可以使Sr2Al2SiloN1404在无压条件下以1600℃的温度成相。其激发光谱位于340nm,半高宽范围为280nm-400nm；发射谱范围为508-540nm。激发谱和发射谱发生红移的原因是因为Sr取代了Ba,导致了晶格的收缩以及稀土离子周围配位环境的变化。3、Ca2Al2Sil0N1404相在常压下无法成相,但是Ca可以对Ba2Al2SiloNl404相进行一定量的掺杂。由于Ca的半径较小,所以Ca的引入导致了晶格的收缩,引起晶格场强度增加,从而使Eu2+的5d能级分裂加剧。因此电子从5d能级跃迁到4f能级产生的发射光谱相对于Ba2Al2SiloNl404;Eu2+有较大的红移,由Ba2Al2SiloN1404：Eu2+中的476nm-527nm红移至527nm-555nm。由于晶格的收缩,Eu2+之间能量传递的增加导致在Ca掺杂的Ba2Al2Si1oN1404：Eu2+中的Eu2+的淬灭浓度也减小。同时由于Ca的掺杂有助于Ba2Al2Sil0N1404：Eu2+的成相,所以随着Ca含量增加,其发射光谱强度也增加,但是只能限制于Ca的最大掺杂量之内。4、通过改变Ba2AlXSi12-XNl6-x02+X：Eu2+中x值来调整其氮氧比例,得到了当x=6时的Ba2Al6Si6N1008：Eu2+有良好的发光性能。其激发峰覆盖了250nm-420nm范围,发射峰位于470nm,发射峰的强度已经达到普通YAG粉的两倍。第四章探讨了一种新型MgYSi205N基荧光材料的性能,通过高温固相反应合成了系列纯相。对MgYSi205N：Ce3+,Mn2+的发光性能研究时发现：1、在MgYSi205N只掺入Ce3+时在289nm和324nm有激发峰出现,而在发射波段有很强的蓝光发射,发射波长位于400nm,可以明显看到两个较近的发射峰出现。这是因为Ce3+的4f1能级存在双重态2F7／2和2F7／5而产生的。在通过增加Ce3+的含量发现当Ce3+掺杂达到30%时就无法保持纯相而产生杂相。在只掺入Mn2+的情况下没有荧光现象出现。2、在MgYSi205N共掺入Ce3+和Mn2+时,激发光谱相对于未掺入Mn2+时产生红移的现象,由289nm和324nm红移至304nm和355nm,由于355nm与紫外LED365nm的发射波长相近,所以使得MgYSi205N：Ce3+,Mn2+能够和紫外LED更好的匹配。在MgYSi205N：Ce3+,Mn2+中出现了两个波段的发射波,分别位于蓝光波段和红光波段,蓝光波段来自于Ce3+,而红光波段来自于Mn2+的发射,说明在Mn2+掺入后有能量传递的现象出现。并且能量传递发生的同时,Mn2+掺入还增强了Ce3+的蓝光发射强度。在红光波段有602nm和673nm两个发射波段的出现,当在低Mn2+浓度时主要以602nm的发射光为主,这主要来自于4T1(4G)→6A1(6S)能级的跃迁,而在高浓度时以673nm的发射光为主,这主要是由于高浓度时形成Mn2+-Mn2+的离子对或者Mn2+离子团簇,其发光相对于单个Mn2+离子红移。3、通过Lu3+和Zn2+对于MgYSi205N：Ce3+,Mn2+发光性能的影响发现：Lu3+的掺入可以使蓝光波段的发射光得到增强,但是红光波段受到抑制,原因在于Lu3+的掺入影响了Ce3+,Mn2+之间能量传递的发生。而掺入Zn2+时发现Zn2+对于Mn2+的两个红光波段的发射有影响,这是由于Zn2+掺入影响到Mn2+离子之间的能量传递。第五章结合CIE色度坐标图分析了利用Ba稳定的Sr2Al2Sil0N1404：Eu2+和MgYSi205N：Ce3+,Mn2+和紫外LED来合成白光的可能性,对其应用前景进行了展望。最后对全文进行了总结。更多还原

【Abstract】 Since 1996, the Nichia Company developed the white LED based on the InGaN chip. A lighting revolution is sweeping all over the world. The white light LED has many advantages, such as superior lifetime, efficiency, reliability and designable, compared with the fluorescent and conventional incandescent lamps.Due to the luminescent mechanism of semiconductor, one LED chip could not emit white light. There are three fundamental ways of generating white light in white light LED:(1) Combination of red, green, blue-LED chips, but the techniques and controlling system are very complex. (2) Combination of a yellow phosphor with the blue LED chip, such as YAG:Ce3+phosphor and GaN chips. The emission of LED was absorbed by the phosphor, which can reduce the hurt of the ultraviolet radiation and the waste of emission energy. (3) Combination of three primary color phosphors which can be excited by an ultraviolet (UV) LED. This three-converter system is improved in color rendering and directionality, compared to the white light LED composed of a yellow phosphor and blue emission LED. Much interest currently exists in down-converting phosphors for application in white light LED.The phosphor is very important in white light LED. Traditional phosphors usually based on the sulfide, aluminate and silicate. Recently, the rare-earth doped (oxo)nitridosilicate phosphors have attracted much attention, for example Sr2Si5N8:Eu2+, Ca-α-SiAlO:Eu2+. In (oxo)nitridosilicate phosphors, the nephelauxetic effect and the relative low electronegativity value of N3" ion cause the large splitting of 5d energy levels, which make the redshift of the excitation and emission band, so it make them as a potential candidate for the UV-LED and blue LED. The (oxo)nitridosilicate phosphor also have the advantages of better flexibility, composition-tunability and higher thermal and chemical stability. This thesis focuses on the preparation of the new (oxo)nitridosilicate phosphor. We studied their structure, luminescence properties and the potential of application in the white light LED.This thesis consists of five chapters. Chapter 1 introduces the lighting history especially about the White-Light-LED. Chapter 2 is experimental procedure. Chapter 3 and chapter 4 studied the M2Al2Si10N14O4 and MgYSi2O5N based phosphors respectively. Chapter 5 discusses their portential of application in white light LED.In chapter 3, we prepared the Ba2Al2Si10N14O4, Sr2Al2Si10Ni4O4 and Ca2Al2Si10N14O4 based phosphors by solid-state reactions. Their properties were studied in terms of XRD, SEM and light-conversion properties. Following is some conclusions:1. The pure Ba2Al2Si10N14O4 phase could be prepared at 1600℃under latm N2 atmosphere. The excitation band of Ba2Al2Si10N14O4:Eu2+ is located in 300nm and covers the 270nm-350nm region. The emission band is located at 476nm-527nm depending on Eu2+concentrations.2. The Sr2Al2Si10N14O4 can not be prepared at 1600℃under latm N2 atmosphere, but pure Sr2Al2Si10N14O4 phase could be obtained with the addition of only 1 wt%Ba. Compared with the Ba2Al2Si10N14O4:Eu2+, the excitation band of Ba stabilized Sr2Al2Si10N14O4:Eu2+redshifts to 340nm and covers the 280nm-400nm region, the emission also redshifts to the 508-540nm. The reason of redshift is the coordination changed due to the substitution of Ba with Sr.3. Pure Ca2Al2Si10N14O4 can not be synthesized, but the substitution of Ba with Ca can adjusting the photoluminescence properties of Ba2Al2Si10N14O4. The highest Ca incorporation is 20% of Ba based on XRD measurement. In the Ca doped Ba2Al2Si10N14O4:Eu2+, when the Ca occupy the Ba, the crystal field around the Eu2+ changed, which cause the large splitting of 5d energy levels, the energy gap between 5d and 4f energy levels is decreased. So the emission redshifts from 476nm-527nm of Ba2Al2Si10N14O4:Eu2+to 527nm-555nm of 20% Ca incorporated Ba2Al2Si10N14O4: Eu2+ phosphor. Because of the shrinkage of the crystal lattice, the distance between Eu2+ is small, and the probability of energy transfer increases, so the quenching concentration of Eu2+ is smaller.4、The change of x value can adjusting the ratio of O/N, so the luminescence properties of Ba2AlxSi12-xN16-xO2+x:Eu2+ will change with the x value. There is a broad excitation band of Ba2Al6Si6N10O8:Eu2+ which covers 250nm-420nm. The emission band is 470nm and the intensity of emission nearly twice higher than the YAG:Ce3+. In chapter 4 we synthesized the MgYSi2O5 by the solid-state reaction method and studied the luminescence properties of MgYSi2O5:Ce3+, Mn2+phosphors. We discovered that:1. There were two excitation bands in the MgYSi2O5:Ce3+, which located 289nm and 324nm respectively. There is a blue doublet emission band at 400nm. The doublet emission due to transitions from the lowest 5d level to the 2F5/2 and 2F7/2 spin-orbit split 4f ground state level of Ce3+.2. We studied the luminescence properties of MgYSi2O5N:Ce3+,Mn2+, there are blue and red emission bands at 400nm and 600nm-700nm respectively while there is only blue emission band in the MgYSi2O5N:Ce3+, it confirms the effective resonance-type energy transfer from Ce3+to Mn2+. The excitation spectra of both phosphors composed of a double excitation bands and redshift occurs with the incorporation of Mn2+. We also discovered that the Mn2+ can enhance the blue emission of Ce3+. There are two emission bands of Mn2+, one is located at 603nm and the other is located at 672nm. The 602nm emission dominates at low Mn2+ concentration, while the 673nm band dominates at higher Mn2+concentrations, due to the energy transfer between Mn2+ions.3. The luminescence properties of Lu3+or Zn2+ doped the MgYSi2O5N:Ce3+, Mn2+ phosphors were also studied.In chapter 5, we concluded the previous results, and studied how to obtain white light by the combination of the Sr2Al2Si10N14O4:Eu2+and MgYSi2O5N:Ce3+, Mn2+ phosphors with a UV-LED.更多还原