白光LED用Ce∶YAG微晶玻璃的研究进展

Ce∶YAG微晶玻璃是一种可替代荧光粉用于白光LED的新型高性能荧光材料。综述了YAG微晶玻璃的制备方法、性能影响因素、发光机理,指出了Ce∶YAG微晶玻璃应用于白光LED的优势,并展望了白光LED用YAG微晶玻璃的发展趋势。     

烧结温度对硼硅基质荧光玻璃发光性能影响

采用共烧结法制备了硼硅基质Ce: YAG荧光玻璃,研究了烧结温度在600℃~900℃范围内, Ce: YAG荧光玻璃的发光强度变化和色坐标漂移规律。结果表明, 随着烧结温度的升高, Ce: YAG荧光玻璃发光强度先增强后减弱, 700℃烧结时, 荧光玻璃获得最大发光强度; 超过850℃烧结时, 荧光玻璃无发光性能; 同时, 色坐标(x, y)发生漂移, 且比相同烧结温度的荧光粉漂移幅度大。通过X射线粉末衍射仪、差示扫描量热分析仪和X射线光电子能谱分析仪测试分析表明: 随着烧结温度升高, 荧光粉中的Ce³⁺被玻璃基质氧化成Ce⁴⁺, 玻璃液体腐蚀破坏了荧光粉YAG晶体结构, 降低了荧光玻璃的发光强度, 从而导致色坐标劣化漂移。     

复合钇铝石榴石荧光粉微晶玻璃发光性能影响因素分析

发光玻璃在白光LED照明等技术领域有重要应用,研究发光玻璃可以有效提高LED器件的发光效率。对复合钇铝石榴石(YAG∶Ce)荧光粉磷锌硼系(PZB)微晶玻璃的发光性能影响因素进行了分析研究。利用荧光光谱等表征手段,通过正交实验方法,讨论了基质玻璃成形方式、荧光粉掺入量和烧结气氛等对微晶玻璃发光性能的影响。研究表明,基质玻璃成形方式和荧光粉掺量对微晶玻璃的发光性能有较大影响:水淬法制备的基质玻璃的发光性能优于浇注法制备的基质玻璃;当荧光粉掺量为20%(质量分数)时,相对发光强度最大,而后又趋于下降;而烧结气氛对发光性能影响不大。采用正交实验法,得出微晶玻璃试样的相对发光强度范围为1 081~4 577,各因素对发光强度影响顺序为荧光粉掺量基质玻璃成形方式烧结温度烧结气氛。     

Ce、Cr∶YAG微晶玻璃的制备及光谱性能研究

目前白光LED在红光波段发射较弱,导致其显色指数偏低,在白光LED用Ce∶YAG微晶玻璃中掺入Cr3+来增强红光波段的发射,从而提高显色指数。通过X射线衍射、荧光光度计、电光源参数测试对样品的晶相、光谱性能及荧光寿命进行了表征。研究了Cr3+对Ce∶YAG微晶玻璃发光性能的影响,并对其增红机理进行了初步的探讨。结果表明基质玻璃在1400℃热处理可析出纯的YAG晶相;Ce∶YAG和Ce、Cr∶YAG微晶玻璃在460nm激发下,在480～650nm产生有效发射,发射光谱中心波长位于530nm;由于Ce3+(2E)-Cr3+(4T)之间的非辐射能量传递,Ce、Cr∶YAG微晶玻璃在688、692和705nm处有红色发射峰,能有效地提高白光LED的显色性能。     

掺杂对白光LED用YAG：Ce荧光粉发光性能的研究

采用高温固相法合成了YAG：Ce荧光粉，研究了掺杂元素对YAG荧光粉发光性能的影响。研究表明：YAG：Ce荧光粉亮度随着Ce含量增加先上升后下降。Sm的掺杂对荧光粉发射光谱峰位无影响，而发光亮度却明显下降。随着Gd掺入量的提高，YAG荧光粉的发射光谱发生红移，发光亮度有所下降。YAG：Ce荧光粉的发射光谱，随着Lu掺入量的提高，发射光谱发生蓝移，发光亮度略有下降。在YAG：Ce中掺入Pr，发射光谱在610nm处出现尖锐的红峰，但随着Pr掺入量的增加，亮度明显下降。     

Ce:YAG荧光陶瓷掺杂Gd对白光LED发光性能的影响

Ce: YAG荧光陶瓷具有突出的导热性及化学稳定性, 相比有机硅胶封装法在高功率白光LED的应用上具有更广阔的应用前景。本研究采用真空固相烧结法制备了不同Gd掺杂浓度的(Gd, Y)₃Al₅O₁₂:Ce样品, 通过XRD, SEM及荧光光谱等表征手段, 研究了Gd掺杂对Ce:YAG荧光陶瓷的晶体结构及其用于白光LED时对发光性能的影响。实验表明, 随着Gd掺杂浓度的提高, Gd³⁺取代Y³⁺ 的位置进入晶格, 使得样品的晶格常数增加。Gd³⁺还影响了Ce³⁺对蓝光的吸收, 同时Ce³⁺将蓝光转换成黄光的效率也下降, 导致光效从81.45 lm/W降低至63.70 lm/W。Gd的掺 杂使Ce³⁺的光致发光谱峰位从534 nm向564 nm红移, 显色指数从61.3提升至70.2。Gd的掺杂虽然降低了发光 效率, 但显著提高了(Gd, Y)₃Al₅O₁₂:Ce样品的显色指数, 使得黄色YAG荧光陶瓷应用于白光LED的性能得到了 提高。     

喷雾干燥-高温热处理两步法制备YAG∶Ce~(3+)荧光粉

以喷雾干燥-高温热处理两步法,由含聚合铝阳离子的前驱体悬浊液,制得了YAG∶Ce3+荧光粉。用XRD、SEM、荧光光谱等研究了热处理温度、前驱体悬浊液浓度对YAG晶相的形成、粉末颗粒形貌及发光性能的影响。发现前驱体悬浊液浓度由0.03mol/L提高到0.09mol/L时,热处理后所得荧光粉颗粒尺寸增大,并趋近球形;前驱体悬浊液浓度为0.09mol/L,热处理温度从1300℃提高到1500℃时,荧光粉相对亮度提高。YAG∶Ce3+粉末900℃热处理2h可获YAG相;所制备的YAG∶Ce3+荧光粉颗粒无空心,团聚程度低。     

Ce-YAG微晶玻璃的制备及其发光性能

采用高温固相熔融法在弱还原气氛下制备了Ce3+离子掺杂的Y2O3-A12O3-SiO2(SAY)系基础玻璃,并在1250℃~1300℃热处理一定时间制备了晶相为YAG的黄色微晶玻璃。通过XRD、SEM研究了微晶玻璃的结构及相组成;激发和发射光谱分析了Ce3+离子在玻璃及微晶玻璃不同基质中的发光特性,以及Al2O3/Y2O3摩尔比对微晶玻璃样品发光性能的影响。结果表明:基础玻璃经热处理能得到Ce-YAG微晶玻璃,晶粒大小在80~120nm范围内,晶粒发育良好。该微晶玻璃样品能被450nm有效激发,并在530nm处有宽带发射峰,归属于Ce3+的5d-4f(2F2/7)。该微晶玻璃在LED照明领域中有很大的应用开发价值。Al2O3和Y2O3的摩尔含量变化对微晶玻璃发光性能有较大影响,在Al2O3/Y2O3的摩尔比为1.5时,样品的发光性能最佳。     

基于荧光膜的大功率白光LED的发光性能

使用荧光粉和硅胶制备荧光膜,然后与455 nm蓝光芯片模组组装成高功率的白光LED器件。采用吸收光谱、荧光光谱和电致发射光谱等对荧光膜和器件进行表征,研究了红色荧光粉与黄色荧光粉的比例对器件性能的影响。结果表明:所制备的荧光膜表面平整、荧光粉分散均匀。Y_3Al_5O_(12):Ce~(3+)(YAG)荧光膜的吸收光谱峰分别位于337 nm和450 nm左右,与YAG荧光粉中Ce~(3+)的f-d跃迁吸收对应,且当荧光膜厚度为1.00 mm时制备出的功率为2.8 W左右的LED模组光色参数较好。将不同比例红色荧光粉和黄色荧光粉按上述厚度和条件制备高显色荧光膜和低色温4460 K、高显色指数91.7的白光LED器件。     

白光LED用YAG∶Ce~(3+)发光材料的性能增强研究

以硼酸和碱土氟化物作为助熔剂,调整助熔剂比例和组分,采用高温固相法合成一系列白光LED用YAG∶Ce3+发光材料。采用XRD、扫描电镜(SEM)和荧光光谱(PL)等对样品进行表征。研究表明,合适的助熔剂有助于降低样品的烧结温度,不会有杂相产生,加入不同浓度和成分的助熔剂对样品的发射、激发光谱形状和峰值波长位置无影响,但对发光强度影响较大;采用助熔剂质量分数为0.4%(0.2%H3BO3-0.2%BaF2)时,所合成样品的颗粒比较均匀,发光性能的增强最为有效。将其和蓝光Ga(In)N芯片封装成白光LED,光效也得到显著提高。封装后白光LED的色坐标为(0.3341,0.4190),色温为5470K,显色指数为67,光效可达到78.3lm/W,高于其它条件合成荧光粉封装的白光LED。     

Effect of metal halide fluxes on the microstructure and luminescence of Y3Al5O12:Ce phosphors

Yellow-emitting Y_2.95Al₅O₁₂:0.05Ce (YAG:Ce) phosphor particles with high luminescence efficiency under 450 nm ultraviolet (UV) excitation were prepared by a heat treatment of submicrometer-sized oxide powder mixture in a reducing atmosphere at 1550 °C. Prior to the heat treatment, the oxide mixture was blended with 5 wt% of metal halides – BaF₂, BaCl₂, NaF, NaCl, and KF – as a flux. It was observed that YAG:Ce particles prepared with fluorine containing flux demonstrated spherical morphology, high photoluminescence properties, and diameters of 5–20 μm, whereas those prepared with chlorine were small-sized particles (≤5 μm) with relatively low intensity. The highest relative photoluminescence (PL) intensity (∼118%) was obtained for the samples prepared with 5% BaF₂. A set of rules was established for the formation of spherical YAG:Ce particles in the presence of this flux.     

紫外发射荧光粉SrCO_3:Ce~(3+)的制备及其发光性质

采用微波辅助共沉淀法制备紫外发射荧光粉Sr1-xCO3:xCe3+,并利用扫描电镜、激光粒度测试、X射线衍射和荧光光谱等分析手段分别对样品SrCO3:Ce3+的形貌、粒径、物相和发光性能进行表征。结果表明:掺杂Ce3+作为发光中心进入到纯斜方晶系碳酸锶晶格中,没有导致晶体结构的变化;样品呈类球状分布,粒径范围3~8μm,中值粒径d50=5.518μm;以254、327 nm波长激发均产生峰值位于354、378 nm的宽发射谱带,位于近紫外发射区,可以应用于黑光灯等;随着Ce3+离子掺杂浓度的增大,发光强度先增加后减小,其淬灭浓度为1.5%(摩尔分数);根据Dexter理论得出样品的浓度猝灭机理为电偶极-四极相互作用。     

The study of luminescence properties on Ce:YAG phosphor in glass co-sintered at different temperatures

Ce:YAG phosphor in glass was prepared by co-sintering bismuthate glass frits and Ce:YAG phosphors at different temperatures in the 550–800 °C range. In this work, the effect of co-sintering temperature on the photoluminescence and chromaticity coordinates (CIE) of phosphor in glass was investigated. The results show that the CIE coordinates is tunable with the increase of co-sintering temperature. As temperature increased from 550 to 700 °C, the intensity of emission and excited peak increases until a maximum is reached, after which it rapidly drops off. The degradation of luminescence properties with the higher co-sintering temperature is due to the broken lattice surrounding the Ce³⁺ and oxidation of the Ce³⁺ caused by the reactions between the bismuthate glass and Ce:YAG phosphors.     

Synthesis and luminescence properties of YAG:Ce nanopowder prepared by the Pechini method

Cerium-doped yttrium aluminum garnet (YAG:Ce) powder was synthesized by the Pechini method with aluminum nitride, yttrium nitride, citric acid and ethylene glycol as the starting materials. Structure, morphology and luminescence spectra were investigated by using X-ray diffraction, thermogravimetric and differential thermal analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and photoluminescence spectroscopy measurements. The pure YAG phase was formed after heat treatment at 800 °C for 3 h and no intermediate phase was observed. The average size of the particles was about 70 nm. The photoluminescence spectrum of the crystalline YAG:Ce phosphors showed the green-yellow emission with 5d → 4f transition as the most prominent group.The increase of the ethylene glycol:citric acid molar ratio, resulted in a powder with smaller particle size and better luminescence properties.     

The synthesis and optical property of solid-state-prepared YAG:Ce phosphor by a spray-drying method

Ce³⁺-activated yttrium aluminum garnet (Y₃Al₅O₁₂:Ce, YAG:Ce) powder as luminescent phosphor was synthesized by the solid-state reaction method. The phase identification, microstructure and photoluminescent properties of the products were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), absorption spectrum and photoluminescence (PL) analysis. Spherical phosphor particle is considered better than irregular-shaped particle to improve PL property and application, so this phosphor was granulated into a sphere-like shape by a spray-drying device. After calcinating at 1500 °C for 0, 4, and 8 h, the product was identified as YAG and CeO₂ phases. The CeO₂ phase content is decreased by increasing the calcination time or decreasing the Ce³⁺ doping content. The product showed higher emission intensity resulted from more Ce³⁺ content and larger grain size. The product with CeO₂ was found to have lower emission intensity. This paper presents the crystal structures of Rietveld refinement results of powder XRD data.     

Synthesis and characterization of photoluminescent cerium-doped yttrium aluminum garnet

Powder phosphor yttrium aluminum garnet (YAG), doped with trivalent cerium (Ce³⁺) is synthesized by sol-gel method. The formation of YAG and YAG:Ce (cerium-doped yttrium aluminum garnet) was investigated by means of X-ray diffraction (XRD). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were also used. The purified crystalline phases of YAG and YAG:Ce were obtained at 1000 °C. The maximum average grain size is about 20-23 nm for undoped samples and 28-34 nm for doped samples. The crystalline YAG:Ce emission shows one peak in the range 480-535 nm with the maximum near 520 nm. Photoluminescence (PL) intensity of 5d → 4f transition of Ce³⁺ increased with increasing annealing temperature. With increasing the concentration of Ce³⁺, the photoluminescence peak shifts towards the red region.     

撞击流共沉淀法制备YAG:Ce荧光粉过程的研究

采用Al(NO3)3、Y(NO3)3和Ce(NO3)3为母盐,碳酸氢铵为沉淀剂,利用撞击流共沉淀法制备YAG:Ce(Y3Al5O12:Ce)球形纳米粉体。利用XRD、FT-IR、SEM和荧光分光光度计对YAG前驱体及煅烧纳米粉体进行了表征,并分析了母盐溶液的浓度、溶液的滴加速度以及煅烧方法和温度对制备YAG纳米粉体的影响。结果表明母盐溶液的浓度、滴加速度及煅烧方法和温度对煅烧粉体的组成、分散性、形貌及发光性能有显著的影响。当初始原料浓度较低(c0=0.055mol/L)时,900℃可以获得纯YAG晶相,不形成任何中间相;初始浓度c0在1.0mol/L以上时,1000℃得到的YAG荧光粉中有YAM、YAP和CeO2杂质相存在;适当的提高加料速度,可以增加粉体的结晶度;采用Na2CO3-S-K2CO3助熔剂辅助煅烧,700℃时已完全转变为YAG相,与直接煅烧法相比,YAG相的完全转变温度降低了约300℃,荧光粉的发光强度比不加熔盐明显提高了。