YAG:Ce^(3+)@SiO_2核壳结构荧光粉制备及荧光特性

以碳酸氢铵和氨水混合溶液为沉淀剂,采用甲醇辅助共沉淀法制备以SiO_2为核、YAG:Ce^(3+)为壳的核壳结构YAG:Ce^(3+)@SiO_2纳米荧光粉。采用热分析(TG-DTG)、X射线粉末衍射(XRD)、透射电镜(TEM)、荧光光谱(PL)对粉体进行表征。XRD表征结果表明,前驱体经过1 000℃煅烧3 h制备的YAG:Ce^(3+)样品为YAG纯相,YAG:Ce^(3+)@SiO_2样品为YAG相和SiO_2相。TEM表征结果表明,YAG:Ce^(3+)@SiO_2核壳结构中SiO_2核的大小为30~40 nm、壳厚约为10 nm。YAG:Ce^(3+)@SiO_2荧光粉激发光谱为双峰结构,主要激发峰为451 nm,与Ga N的蓝光发射匹配;发射光谱为一宽带,主峰波长为525 nm,能与Ga N的蓝光组合形成高亮度白光。而且YAG:Ce^(3+)@SiO_2的激发光谱和发射光谱的强度比YAG:Ce^(3+)粉体强。

LED用YAG:Ce^(3+)荧光粉包覆SiO_2膜的研究

选用热稳定性好、无色透明的SiO2为包覆物,采用溶胶法,以正硅酸乙酯(TEOS)为硅源,对YAG:Ce3+荧光粉的表面进行SiO2膜的包覆研究,以解决LED荧光粉在使用过程中突出的热劣化问题。采用X射线衍射(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM)和荧光光谱(FS)等对包膜前后的YAG:Ce3+荧光粉的晶体结构、表面形貌、发光性能等进行表征和分析。结果表明,YAG:Ce3+荧光粉表面上包覆了一层均匀且致密的氧化硅膜层,且对包膜后的YAG:Ce3+荧光粉的发光性能基本没有影响,包覆效果较好。

Al_2O_3对白光发光二极管用YAG∶Ce荧光粉的影响研究

采用高温固相法合成了YAG∶Ce荧光粉,考察了、、三种相态的氧化铝对制备YAG∶Ce荧光粉结晶度及发光性能的影响,确定了-Al2O3作为生产YAG∶Ce荧光粉的原材料;同时对比研究了不同生产工艺获得-Al2O3的颗粒形貌、粒度分布等物理性能对荧光粉形貌、粒度、色品坐标、发射主峰及相对亮度的影响,确定了选用异丙醇铝法生产的球形Al2O3为原材料。将YAG∶Ce荧光粉与蓝光芯片混合封装成色温为(5 238±50)K的白光发光二极管(LED),在100 mA电流激发下,光效138.32 lm/W、显色指数a=70.1。

Composite structure Al_(2)O_(3)/Al_(2)O_(3)-YAG:Ce/YAG ceramics with high color spatial uniformity for white laser lighting

Composite ceramic phosphor(CCP)is a candidate light-conversion material to obtain the high-quality laser lighting source.Phosphors based on the transmissive configuration model could not simultaneously meet the requirements of angular color uniformity and high thermal stability.In this study,a novel composite structure ceramic was designed,including Al_(2)O_(3)-YAG:Ce/YAG layered ceramic with a size of 1 mm×1 mm for lighting,and Al_(2)O_(3) ceramic(φ=16.0 mm)was used as the wrapping material due to its outstanding thermal stability.The prepared ceramics exhibited excellent thermal performance and no yellow ring phenomenon.Through this design,we achieved the match of the intensity distribution of the blue and yellow lights,resulting in a high angular color uniformity of 0.9 with a view angle of±80°.All ceramics showed no luminous saturation phenomenon,even the laser power density was increased up to 47.51 W/mm^(2).A high-brightness white-light source with a luminous flux of 618 lm,a luminous efficiency of 126 lm/W,a CCT of 6615 K,and a CRI of 69.9 was obtained in the transmissive configuration.In particular,the surface temperature of the ceramic was as low as 74.1℃ under a high laser radiation(47.51 W/mm^(2)).These results indicate that Al_(2)O_(3)/Al_(2)O_(3)-YAG:Ce/YAG composite structure ceramic is a promising luminescent material in the high-power laser lighting applications.

Ce∶YAG单晶复合红色荧光粉的制备及其在白光LED上的应用

采用提拉法生长了Ce∶YAG单晶,并以Ce∶YAG单晶取代传统Ce∶YAG荧光粉用于制备白光发光二极管(LED),研究了Ce∶YAG单晶厚度的变化对其色坐标、亮度、发光效率和色温的影响。由于460 nm蓝光芯片激发的Ce∶YAG单晶白光LED缺少红光成分,采用流延法将红色荧光粉CaAlSiN_3∶Eu^(2+)涂覆在Ce∶YAG单晶衬底上制备白光LED。制备的白光LED色度随红粉含量的变化由冷白光逐渐向暖白光区域移动,色温逐渐降低、显色指数上升。研究结果表明Ce∶YAG单晶复合红色荧光粉的方式可以应用于大功率LED照明。

含硼助熔剂对YAG∶Ce荧光粉晶相、形貌及发光性能的影响

采用高温固相法分别以H3BO3和Na2B4O7作为助熔剂合成了Ce离子掺杂的Y3Al5O12(YAG∶Ce)黄色荧光材料。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、荧光分光光度计(PL)对合成出的YAG∶Ce样品进行了表征,在此基础上研究了H3BO3和Na2B4O7助熔剂浓度对YAG∶Ce的晶相、微观形貌及光学性能的影响。结果表明,随着H3BO3的增加,发光强度先增大后降低,并且当H3BO3用量为1.5wt%时,发光强度达到最大,同时颗粒分散性最好;然而当增加Na2B4O7用量时,发光强度先增强再降低,晶体发育程度及颗粒分散性先改善再恶化,当用量为6.0wt%时,发光强度最大,颗粒分散性最优。此外,含硼助熔剂由于B离子的引入,有效地提高了YAG晶体对发光中心Ce离子的容纳量。H3BO3和Na2B4O7使Ce离子猝灭浓度分别提高到了0.15和0.10。

Reactive SPS of Al_(2)O_(3)–RE:YAG(RE=Ce;Ce+Gd)composite ceramic phosphors

Ultrafine-grained Al_(2)O_(3)–rare earth:yttrium aluminium garnet(Al_(2)O_(3)–RE:YAG)(RE=Ce;Ce+Gd)composite ceramics were obtained for the first time by reactive spark plasma sintering(SPS)using commercially available initial oxide powders.The effect of key sintering parameters(temperature,dwell time,and external pressure(P_(load)))on densification peculiarities,structural-phase states,and luminescent properties of composites was studied comprehensively.Differences in phase formation and densification between Ce-doped and Ce,Gd-codoped systems were shown.Parameters of reactive SPS,at which there is partial melting with the formation of near-eutectic zones of the Al_(2)O_(3)–YAG system/coexistence of several variations of the YAG-type phase,were established.Pure corundum–garnet biphasic ceramics with an optimal balance between microstructural and luminescence performance were synthesized at 1425℃/30 min/30–60 MPa.The external quantum efficiency(EQE)of the phosphor converters reached 80.7%and 72%with close lifetime of~63.8 ns,similar to those of commercial Ce:YAG materials,which is promising for further applications in the field of high-power white light-emitting diodes(WLEDs)and laser diodes(LDs).

YAG荧光粉的表面改性及其发光和热/湿劣化性能研究

采用高温固相法合成了YAG:Ce^(3+)黄色荧光粉,基于Stober法的包覆技术对YAG:Ce^(3+)进行了SiO_2包覆实验,研究了表面包覆对荧光粉发光特性的影响;并系统探讨了YAG:Ce^(3+)@SiO_2荧光粉的耐高温高湿性能.研究表明,通过改进包覆工艺实现了形貌均匀的YAG:Ce^(3+)@SiO_2核-壳荧光粉;当包覆粒径在100nm左右时,粉体表面缺陷改善,发光强度相对于YAG:Ce^(3+)荧光粉提高了34%;设计并实现了高温高湿实验,在相同实验条件下与YAG:Ce^(3+)荧光粉对比,YAG:Ce^(3+)@SiO_2荧光粉在180℃时的发光强度衰减减小了4%,同时在180℃对应的湿度条件下,发光光谱强度衰减减小了8%.这表明,表面改性技术有效地改善了荧光粉的热稳定性和耐湿性,将有效促进蓝光芯片激发黄光荧光粉的白光LED在室外大功率照明中的应用.

钨酸锂铕荧光粉封装性能的研究

文章介绍了获得白光LED的几种主要方法,并研究了钨酸锂铕(LiEuW2O8)与YAG:Ce3+的不同配比组合封装对白光LED的光效、色温、显色指数等的影响。结果显示,随着LiEuW2O8含量从60%增至90%,显色指数升高到86,但是光效下降了近20 lm/W,色温也大幅升高至15 000K。分析原因,作者认为这主要是由于荧光粉的发光效率偏低造成的。