【作者】 刘红利；

【导师】 许并社；

【作者基本信息】 太原理工大学 ， 材料科学与工程， 2013， 博士

【摘要】 利用近紫外激发的三基色荧光粉实现白光LED已成为当前发展的重点,探索与之相匹配的荧光粉也就成为人们广泛关注的课题。但目前可供选择的近紫外激发的三基色荧光粉种类很有限,而且存在发光效率低、热稳定性差等不足。针对上述问题,根据当前LED用荧光粉的发展需要,本文以具有良好的化学稳定性和热稳定性的正硅酸和偏铝酸盐为基质,以稀土离子做为激活剂,制备两类近紫外激发(NUV:near ultraviolet)的白光LED用荧光粉,并采用化学制备方法改进粉末颗粒粒径、形貌及分散性,系统地研究了基质成分,晶体结构,电子能带结构以及制备工艺等对发光性能的影响。具体研究结果如下：对于正硅酸盐基荧光粉体系：(1)采用固相法制备了可被NUV激发的红色荧光粉M2SiO4:Eu3+(M=Ca, Sr, Ba),并研究了其晶体结构和发光性能的关系。M2SiO4中存在两种碱土离子格位：M(Ⅰ)(非反演对称)和M(Ⅱ)(反演对称)。在Ba2SiO4中,Eu3+主要取代M(Ⅰ),其发射以5D0→7F2(613nm)电偶极跃迁为主。在Ca2SiO4:Eu3+和Sr2Si04:Eu3+中,Eu3+取代M(Ⅰ)和M(Ⅱ)几率相等,其发射以5D0→7F1(591nm)磁偶极跃迁和5D0→7F2(613nm)电偶极跃迁为主。在该类荧光粉中,Ba2SiO4:Eu3+的激发和发射最强,色纯度最好。(2)研究了制备温度、Eu3+浓度及电荷补偿剂对Sr2Si04:Eu3+和Ba2Si04:Eu3+发光性能的影响。当制备温度为1300℃时,样品的发光强度最大。在Sr2SiO4:Eu3+中,Eu3+的猝灭浓度为6%,在Ba2SiO4:Eu3+中,Eu3+的猝灭浓度为8%。电荷补偿剂Li+,Na+和K+的引入均增强了荧光粉的发射强度,其中,Li+效果最好。(3)采用溶胶凝胶法制备了Sr2SiO4:Eu3+和SiO2@Sr2SiO4:Eu3+核壳结构复合发光材料。溶胶凝胶法较高温固相法制备的Sr2SiO4:Eu3+样品结晶温度低,发光强度大,颗粒分布均匀。SiO2@Sr2SiO4:Eu3+样品形貌为单分散球形,其发光强度优于Sr2SiO4:Eu3+。(4)研究了Sr2SiO4:Ce3+和Sr2Si04:Eu2+的发光特性,在长波紫外激发下两个样品均呈双峰发射。Sr2Si04:Ce3+的两个发射峰为406nm和436nm, Sr2Si04:Eu2+的两个发射峰为462nm和535nm,利用Sr2Si04的晶体结构解释了短波长的峰来源于Ce3+/Eu2+取代9配位的Sr(Ⅰ),较大波长的峰来源于Ce3+/Eu2+取代10配位的Sr(Ⅱ)。对Sr2Si04:xEu2+研究发现：随着Eu2+浓度的增加,蓝光发射峰减弱,绿光发射峰增强,主发射峰发生红移(535nm→569nm)。采用第一性原理从理论上分析了Sr2SiO4的电子结构及基质的吸收。对于铝酸盐体系：(1)采用溶胶凝胶法制备了能被NUV激发的SrAl2O4:Eu2+绿色荧光粉,研究了制备温度和Eu2+浓度对其发光性能的影响。结果表明：当温度为1200℃和Eu2+浓度为8%时样品的发射强度最大。当温度超过1200℃,样品中出现Sr4Al14025杂相,导致发射光谱产生蓝移(519nm→509nm)。(2)研究基质组分变化对Eu2+发射的影响。B3+置换SrAl2O4中的Al3+,可使基质晶相发生转变(从SrAl2O4、Sr4Al14O25到SrAl2B2O7),发射波长产生蓝移(519nm→467nm)。Ca2+和Ba2+置换SrAl2O4中Sr2+,可在全组分内形成SrAl2O4、CaAl2O4和BaAl2O4固溶体,实现Eu2+的蓝光(440nm),蓝绿(490nm)及绿光(519nm)发射。其它硼酸盐红色荧光粉：通过固相法制备的LiSrBO3:Eu3+荧光粉在395nm激发下发射峰值为613nm的红光。电荷补偿剂Li+的引入大大提高了其发射强度。另外,Al3+的掺杂改善了LiSrBO,:Eu3+的色纯度,当Al3+掺杂浓度为2%时,其色坐标最好为(0.658,0.342)。更多还原

【Abstract】 At present, using a NUV LED chip coated red, green and blue phosphors has become the emphasis direction to generate white LED. Therefore, to explore tricolor phosphors that can be excited effectively by near UV LEDs (NUV) has attracted substantial attention. However, these types of tricolor phosphors are not much, being the drawbacks of low luminous efficiency and bad thermal stability. To solve the problems, two types of phosphors obtained by RE ions doped in orthosilicate and meta-aluminate hosts with stable thermal and chemical properties were prepared, and size, morphology and dispersion of the phosphors particles are improved by using chemical synthesis method in the paper. The effects of crystal structure, electronic band structure, and synthesis method on luminescent properties were systematically investigated. The main achievements are as the follows:1. A system of Rare earth doped orthsilicate phosphors:(1)M2Si04:Eu3+(M=Ca, Sr, Ba) red-emitting phosphors were synthesized by solid state reaction and these luminescent properties were investigated. M2Si04have two different cation sites:M(Ⅰ)(asymmetric) and M(Ⅱ)(symmetric). In the Ba2Si04:Eu3+, Eu3+mainly occupied at M(I) cation, causing the613nm emission of5D0→7F2strongest. In the Ca2SiO4:Eu3+and Sr2SiO4:Eu3+, it was equal probability that Eu3+occupied at M(☉) and M(Ⅱ) site, which made the transition5D0to7F1(591nm) was as strong as the transition5D0to7F2(613nm). Ba2SiO4:Eu3+phosphor had stronger excitation and emission intensity with better red color purity when compared with Sr2Si04:Eu3+and Ca2SiO4:Eu3+phosphors.(2)The influence of annealing temperature, Eu3+dopant content and charge compensation (Li+, Na+, K+) on intensities of Sr2Si04:Eu3+and Ba2SiO4:Eu3+were studied. When annealing temperature was1300℃, the emission intensity of the samples reached maximum.The quenching content of Eu3+was6%and8%in the Sr2SiO1:Eu3+and Ba2SiO4:Eu3+,respectively. The charge compensator R+(R+=Li+,Na+and K_)injecting into the host efficiently enhanced the luminescence intensity,and the emission intensity of the phosphor doping L+was higher than that of Na+or K+(3)Sr2SiO4:Eu+and SiO2@Sr2SiO4:Eu3+core-shell phosphor were prepared by sol-gel method. Compared with the sample synthesized by solid state reaction, Sr2SiO4:Eu3+had possessed low crystal tempreture, strong emission intensity. SiO2@Sr2SiO4:Eu3+was composed of uniform coating and smooth shell, the emission intensity of SiO2@Sr2SiO4:Eu3+core-shell phosphor was higher than Sr2SiO4:Eu3+ (4) The luminescent properties of Sr2SiO4:Ce3+and Sr2SiO4:Eu2+were investigated. Two samples showed two emission peaks under NUV excitation. The two emission peaks of Sr2SiO4:Ce3+were406nm and436nm, respectively. The two emission peaks of Sr2SiO4:Eu2+were463nm and535nm. Ce3+/Eu2+ions on Sr(I) Sites gave short wavelength emissions, while Ce3+/Eu2+ions on Sr(II) Sites showed an long emission band. With the increasing of Eu content, the blue emission intensity of Sr2SiO4:Eu2+decreased, whereas the green emission intensity increasing. Red shift of emission band from535nm to569nm has been aehieved with the increase of Eu2+content. The electronic structure and host absportion were performed by first principles.2. Eu2+doped meta-aluminate phosphors:(1)The SrAl2O4:Eu2+green-emitting phosphors were synthesized by sol-gel method, and their luminescent properties were investigated with changing the reducing temperature, the concentration of the activator. The highest intensity of SrAl2O4:Eu2+phosphor was achieved by annealing at1200℃and the Eu2+content of8mol%. Over1300℃, however, the Sr4Al14O25phase appeared, inducing a small blue-shift in the emission peak (519nm-509nm).(2) The effects of the host component variety through substituting cation in the host lattice on Eu2+emission spectra were researched. The substitution of B3+for Al3+ions in SrAl2O4host resulted in the transformation of phase from SrAl2O4to Sr4Al14O25as well as to SrB2Al2O7, which led to the blue-shift (519nm-467nm).When Ca2+and Ba2+ions replaced Sr2+ions in the host, SrAl2O4 CaAl2O4and BaAl2O4solid solution can be formed throughout the whole composition range. So, the blue, blue-green and green emitting of Eu2+can be tuned in the hosts.3. Other red borate phosphors:The luminescent properties of LiSrBO3:xEu3+phosphors were studied. This phosphor can be effectively excited by ultraviolet (395nm) and exhibit a satisfactory red performance peaked at around612nm. The introduction of charge compensator Li+, Na+and K+can further enhance emission intensity.The introduction of Al3+improved the color purity of LiSrBO3:Eu3+. When Al3+content was2%, the chromatieity coordinates was (0.652,0.348).更多还原