【作者】 胡小野；

【导师】 李永绣；

【作者基本信息】 南昌大学 ， 无机化学， 2010， 硕士

【摘要】 白光发光二极管(WLEDs)由于具有效率高、寿命长、稳定性高和体积小等诸多优点而受到人们的广泛关注。作为一种很有潜力的固体照明光源,其光效和色度参数以及价格是最为重要的指标。而决定这些指标的是LED芯片外以及涂覆在芯片上的荧光转换材料。本研究致力于合成一些可被蓝光或近紫外光有效激发的新型荧光粉。选择Li2SrSi04:Eu2+和ZnMoO4:Eu3+两类荧光粉为研究对象,通过掺杂来提高该类荧光粉的发光亮度并调谐激发和发射波长。Li2Sr0.995SiO4:0.005Eu2+是一种可被蓝光(400-480 nm)有效激发,发射出主峰在580 nm左右的黄色荧光粉。我们的研究结果证明：通过PO43-和SO42-掺杂均可显著提高发光强度,其最佳组成为Li2Sr0.995(SiO4)0.9775(P04)0.03:0.005Eu2+和Li2Sr0.995(SiO4)0.945(SO4)0.11:0.005Eu2+。在460 nm激发下,它们的发光强度分别是Li2Sr0.995SiO4:0.005Eu2+|的1.8和2.2倍。而且SO42-掺杂还能使激发和发射光谱的最强峰分别由412和580 nm红移到460和610 nm,使其更适合蓝光LED芯片激发并发射红光。将Pr3+掺杂到Li2Sr0.995SiO4:0.005Eu2+中也可以增强其在蓝光(452 nm)的激发效率和在红光区域(610 nm)的发射强度。而且证明Pr3+单掺杂Li2SrSiO4也是一种可被蓝光LED有效激发的红色荧光粉。合成了可被蓝光(466 nm)及近紫外光(395 nm)同时有效激发的ZnMoO4:Eu3+系列红色荧光粉(发射主峰615 nm)。我们的目标是通过掺入Li+作为电荷补偿剂,掺入(Bi3+,Sm3+)或(La3+,Y3+,Gd3+)来替代部分Zn2+,进而提高荧光粉的发光强度和激发峰宽度。证明Li+离子的加入明显提高该粉的发光亮度,其最佳配比为Zn0.5MoO4:Eu3+0.25Li+0.25;适量Bi3+,Gd3+和Sm3+的掺入可以进一步提高发光强度,而且Sm3+的掺入使395 nm的激发峰得到明显的拓宽。据此,得到了性能优异的Zn0.454MoO4:Eu3+0.25Li+0.25Bi3+0.04Sm3+0.006和Zn0.44MoO4:Eu3+0.25Li+0.25Gd3+0.06荧光粉。这些红色荧光粉的激发波长刚好与现有蓝光及近紫外LED芯片光匹配,在以蓝光及近紫外LED芯片为基础的白光LED组装上很有应用潜力。更多还原

【Abstract】 White light-emitting diodes (WLEDs) have been attracted more attention because they have advantages of high luminescent efficiency, long lifetime, reliability, energy savings and small packaging. As for general lighting applications, the luminous efficiency, colorimetric parameters and price of LEDs are of great importance and depend on LED chips used and the phosphors coated on the chips. In our present study, we paid attention to the synthesis of novel phosphors for WLEDs application via blue or near-UV LEDs.Therefore, Li2SrSiO4:Eu2+and ZnMoO4:Eu3+ phosphors were selected as research objects for enhancing luminescence intensity and tuning excitation and emission wavelenghth by doping.Li2Sr0.995SiO4:0.005Eu2+is a yellow phosphor with intense emission peak at 580 nm under excitation of blue light (400-480 nm). Our results showed that co-doping PO43- or SO42- into Li2Sr0.995SiO4:0.005Eu2+enhanced the fluorescence intensity of as-synthesized phosphors. The optimum compositions were determined to be Li2Sr0.995(SiO4)0.9775(P04)0.03:0.005Eu2+and Li2Sr0.995(SiO4)0.945(SO4)0.11:0.005Eu2+ Their luminescent intensity under excitation of 460 nm blue light showed 1.8 or 2.2 times higher than that of Li2Sr0.995SiO4:0.005Eu2+. In addition, the incorporation of SO42- ions also tuned the emission peak from 580 nm to 610 nm and excitation peak from 410nm to 460nm, indicating a novel route to synthesize red phosphors in LED application via blue LED chips. On the other hand, red phosphors under blue light excitation have been synthesized by co-doping Pr3+ into Li2Sr0.995SiO4:0.005Eu2+. The intense emission at about 610 nm is attributed to 3P0-3H6 and 1D2-3H4 transition of Pr3+. Furthermore, we synthesized Pr3+ doped Li2SrSiO4 red phosphors for the first time and demonstrated that these phosphors can be effectively excited by a blue LED chip and emit strong red light, promising that they are important candidates as blue-convertible phosphors for white light-emitting diodes.ZnMoO4:Eu3+ phosphors can emit intense red light at 615 nm when excited by near-UV (about 395 nm) and blue (about 466 nm) light. In order to enhance their luminescent intensity, we doped them with different amount of Li+as charge compensator. The luminescent intensity of as-synthesized phosphors showed that the doping of Li+can obviously improve the emission intensity of Eu3+doped ZnMoO4, and the optimum composition was found to be Zn0.5MoO4:Eu3+0.25Li+0.25·Furthermore, we co-doped Zn0.5MoO4:Eu3+0.25Li+0.25 with different amount of Bi3+, Sm3+or La3+, Y3+, Gd3+for the purpose of of enhancing luminescent intensity and widening excitation band. The luminescence property of as-synthesized phosphors proved that the doping of Bi3+, Sm3+or La3+, Y3+, Gd3+is beneficial for the enhencement of luminescent intensity. Under 395 nm or 466 nm light excitation, the luminescent intensities of as-synthesized phosphors with optimum composition, Zn0.454MoO4:Eu3+0.25Li+0.25Bi3+0.04Sm3+0.006 and Zn0.44MoO4:Eu3+0.25Li+0.25Gd3+0.06 are all over two times higher than that of Zn0.75MoO4:Eu3+0.25. At the same time, the excitation peak at around 395 nm was widened by the doping of Sm3+. These facts indicate that the as-synthesized phosphors promise a potential for the application of light converting to both near-UV and blue LED chips in the fabrications of white light-emitting diodes.更多还原