铈、钐掺杂YAG微晶玻璃制备及光谱性能

以Y2O3-A l2O3-S iO2-L i2O-K2O-Na2O玻璃作为Ce,Sm掺杂基质玻璃,制备出白光LED用YAG:Ce和YAG:Ce,Sm微晶玻璃。利用X射线衍射、荧光光度计对微晶玻璃的晶相、光谱性能及荧光寿命进行了研究。结果表明:掺杂铈或铈钐共掺杂基质玻璃在1400℃热处理得到的几乎是纯YAG晶相;并且YAG:Ce和YAG:Ce,Sm微晶玻璃在454 nm有特征激发峰,说明它们能被蓝光芯片有效激发;在蓝光芯片激发下,YAG:Ce微晶玻璃在480~700 nm产生有效发射,发射光谱中心波长531 nm,同时铈钐共掺微晶玻璃在566,602,615,650 nm都有窄的发射峰,可以提高LED s的显色性、降低色温;此外,浓度掺杂实验表明钐的较好掺杂浓度范围是Ce:Sm为10∶2~10∶10;YAG:Ce和YAG:Ce,Sm微晶玻璃的荧光衰减曲线表明,YAG:Ce微晶玻璃的荧光寿命要长于YAG:Ce,Sm微晶玻璃。     

YAG:Ce,Mn微晶玻璃的制备及光谱性能研究

由于YAG:Ce微晶玻璃缺乏红色发光成分,导致其封装的白光LED显色指数低.以Y2O3-Al2 O3-SiO2-Li2O作为Ce,Mn掺杂的基质,制备了可提高显色指数的白光LED用YAG:Ce,Mn微晶玻璃.通过XRD测试、荧光测试和电光源测试表征了玻璃的晶相结构、光谱性能及荧光寿命,研究了Mn2+对YAG:Ce微晶玻璃发光的影响,并对其增红机制进行了探讨.结果表明:基玻璃在1400℃热处理可析出纯YAG晶相;YAG:Ce,Mn微晶玻璃在460 nm光激发下,在530 nm处有Ce3+的特征发射峰,由于Ce3+-Mn2+之间的能量传递,在585 nm处有Mn2的特征发射峰,从而使得YAG:Ce,Mn微晶玻璃的发光峰比YAG:Ce微晶玻璃的发光峰向红光方向宽化,有效地提高了白光LED的显色性能.     

高掺杂Ce,Gd(Y_(3-x-y)Ce_xGd_y)Al_5O_(12)荧光粉的发光下降及温度猝灭特性

采用高温固相法分别合成了不同Ce浓度掺杂的和固定Ce浓度为0.06不同Gd浓度掺杂的Y3Al5O12(YAG)系列荧光粉,通过测量其激发、发射光谱、漫反射光谱、荧光寿命和变温发射光谱,研究了掺杂元素的浓度对荧光粉发光性能的影响以及荧光粉发光的温度猝灭性质。研究结果表明:荧光粉发光强度随着Ce3+掺杂浓度和Gd3+掺杂浓度的提高均呈下降趋势。分析发现,荧光粉发光强度下降并非主要由浓度猝灭所引起,而是由于高浓度掺杂下发生YAG基质与Ce3+对激发光的竞争吸收,导致Ce3+对激发光的吸收量减少,从而影响发光强度。温度实验表明,随着温度的升高,荧光粉发光强度下降。Ce含量的改变对YAG:Ce荧光粉的热猝灭性质影响较小,Gd的掺杂使荧光粉的发射波长向长波方向移动,同时热猝灭现象严重。     

Ce0.6Zr0.035Y0.05O2 和Pr0.6Zr0.35Y0.05O2 固熔体的氧储存能力及氧化-还原性能的研究

测定了Ce0.6Zr0.35Y0.05O2 和Pr0.6Zr0.35Y0.05O2两种固熔体的晶体结构,氧的储存以及氧化-还原性能. XRD结果表明 Ce0.6Zr0.35Y0.05O2主要以立方的Ce0.75Zr0.25O2结构形式存在,此外还有少量的ZrO1.87. 而Pr0.6Zr0.35Y0.05O2则主要以立方的Pr0.60Zr0.40O2结构形式存在.这两种固熔体粒子都为纳米级,具有多孔和较大表面积的特征.将Y3+掺杂到Ce0.6Zr0.4O2 或Pr0.6Zr0.4O2晶格中,可以提高氧空位, Ce4+或Pr4+浓度. H2(和CO)-O2滴定和TPR-再氧化试验表明在这两种固熔体中分别存在着可逆的Ce4+/Ce3+或Pr4+/Pr3+氧化还原能力.基于试验结果,我们得出以下结论,将Y3+掺杂到Ce0.6Zr0.4O2 或Pr0.6Zr0.4O2晶格中可以(1)提高晶格氧的活动能力,(2)提高Ce4+或Pr4+浓度,(3)提高氧的储存能力和(4)Pr0.6Zr0.35Y0.05O2在Redox性能, 晶格氧的活动能力和氧的储存能力等方面优于Ce0.6Zr0.35Y0.05O2.     

用于白光LED的硼铝硅酸盐YAG玻璃陶瓷制备

用共沉淀法制得的Y3Al5O12(YAG)∶Ce3+前驱体,混和H3BO3-SiO2-Al2O3-Na2CO3玻璃初始材料,经过1300℃3h煅烧,得到用于白光LED封装的硼铝硅酸盐YAG玻璃陶瓷。用差热分析(DTA)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)和光致发光(PL)等分析方法对产物进行表征。研究发现Al2O3和YAG∶Ce3+前驱体含量对YAG玻璃陶瓷激发和发射光谱强度有重要影响。结果表明,玻璃陶瓷中晶体为10μm左右的YAG,其激发和发射光谱与标准YAG荧光粉光谱一致。当Al2O3和YAG∶Ce3+前驱体含量分别为初始混合材料质量的11.5%和34.6%时,玻璃陶瓷荧光强度达到最大值。用本文制备的硼铝硅酸盐YAG玻璃陶瓷封装成白光LED,在350mA驱动电流下,色坐标为(0.2934,0.3094),相关色温为8020K,显色指数为75.2。     

有机-无机杂化凝胶法合成YAG∶Ce~(3+)荧光粉的包膜及其稳定性

本文以金属硝酸盐为原料,柠檬酸为配位剂的有机-无机杂化凝胶法来合成掺杂三价铈离子的钇铝石榴石荧光粉,采用X-射线衍射法研究了杂化凝胶在煅烧过程中的相转变机制。结果表明:杂化凝胶在煅烧过程中可以通过两条途径形成Y3Al5O12(YAG)相:一是由无定形Y2O3和Al2O3直接向YAG相的一步相转变;二是由无定型Y2O3和Al2O3经由YAlO3(YAP)和γ-Al2O3向YAG相的两阶段相转变,在900℃得到结晶性好的纯YAG∶Ce3 荧光粉,其最大激发波长为459nm,最大发射峰波长为550nm;在荧光粉表面包覆氧化铝和氧化镧,将使荧光粉的荧光强度稍有降低,但对荧光粉的稳定性有很好的改进作用。     

YAG∶Ce体系中稀土离子掺杂对Ce3+的光谱性能的影响

采用高温固相法合成了一系列的(Y0.95Ln0.01Ce0.04)3Al5O12(简称YAG∶Ce,Ln),系统地研究了此体系中的Ln3 对Ce3 的发光强度的影响.结果表明,在YAG∶Ce的体系中,La3 ,Gd3 ,Lu3 等光学透明离子的少量掺杂对Ce3 的发光强度的影响不大;掺入少量的Pr3 ,Sm3 ,Tb3 ,Dy3 ,Ho3 ,Er3 ,Tm3 等稀土离子,由于它们的能级与Ce3 的能级有交叠,使它们之间存在着竞争吸收或能量转移,对Ce3 的发光有较明显的变化,其中,Pr3 和Sm3 的掺入使其在红光区有发射峰,可以增加YAG∶Ce的红色成分以提高显色性;Nd3 ,Eu3 和Yb3 对Ce3 的发光有严重的猝灭作用.     

Ce/Tb/Sm共掺杂CaO-B2O3-SiO2发光玻璃的白光发射及其发光颜色调控

用高温熔融法制备了Ce/Tb/Sm三元共掺杂的CaO-B2O3-SiO2发光玻璃材料,并使用荧光分光光度计和CIE色度坐标对其光谱学和发光特性进行了研究.结果表明:在374nm激发下,在Ce/Tb/Sm三元共掺杂发光玻璃的发射光谱中同时观测到了蓝光、绿光和红橙光的发射带,这些发射带的混合实现了白光的全色发射显示.此外,Ce/Tb/Sm三元共掺杂发光玻璃的发光颜色随着Tb4O7含量的减小从绿光逐渐过渡到白光,显示出发光颜色的可调节性,极大地扩展了其在白光发光二极管中的应用.     

Ce掺杂K_2La_2Ti_3O_(10)催化剂的可见光高效催化制氢的研究

采用高温固相法合成了铈掺杂的K2La2Ti3O10催化剂,利用X射线衍射(XRD)、紫外-可见漫反射(UV-visDRS)、透射电镜(TEM)和X射线光电子能谱(XPS)对催化剂进行了表征.考察了催化剂的可见光催化分解甲醇水溶液制氢的活性,并对可见光催化机理进行了分析.研究表明,铈的掺杂没有改变K2La2Ti3O10的微晶结构,并使催化剂粒径有所减小.紫外可见漫反射分析表明禁带宽度为2.3eV左右,对可见光具有较高吸收.XPS表明La和Ti为+3和+4价,而Ce则是+3和+4的混合价态.担载2wt%Pt后,在可见光下光催化活性大大提高,当铈的掺杂量为0.5mol%(即Ce取代La的摩尔百分量)时,光催化活性达到最大,产氢速率为0.05mmol/h;光照5h后产氢量为0.22mmol,而纯K2La2Ti3O10的产氢量只有0.037mmol.     

铈掺杂Y3Al5O12热障涂层陶瓷材料的制备与性能研究EI北大核心CSCD

采用高温固相反应合成法制备不同组分的铈掺杂Y3Al5O12热障涂层陶瓷材料，利用X射线衍射仪、X射线光电子能谱、扫描电子显微镜、维氏硬度仪和激光导热仪研究Ce掺杂量对陶瓷材料物相组成、微观形貌、硬度和热导率的影响规律。结果表明：当Ce掺杂量x为0.01和0.02时，(Y1-xCex)3Al5O12呈单一YAG相，(Y0.99Ce0.01)3Al5O12的硬度最大，约为18.93 GPa;(Y0.98Ce0.02)3Al5O12的热导率最低，1000℃时约为1.95W·m-1·K-1。随着Ce掺杂量的增加，材料中出现Ce O2第二相且Ce4+的占比增多，粉体颗粒尺寸增大，陶瓷晶粒尺寸减小，导致(Y1-xCex)3Al5O12陶瓷材料的硬度和热导率均有所下降。     

白光LED用Ce:YAG单晶的光学性能与掺杂浓度分析

采用提拉法生长Ce∶YAG单晶,通过X射线衍射和激发发射光谱对其晶相结构和光谱特性进行了表征,研究了Ce∶YAG单晶封装白光LED的最佳掺杂浓度.在455 nm蓝光激发下,Ce∶YAG单晶的发射光谱可由中心波长526 nm(5d12E gГ8g→4f12F7/2Г8u)的宽发射带(500~650 nm)组成;激发光谱由343 nm(4f12F5/2Г7u→5d1 2E gГ7g)和466 nm(4f12F5/2Г7u→5d1 2E gГ8g)2个激发峰组成;Stokes位移为2448 cm-1,Huang-Rhys因子为6.12.研究结果表明,Ce∶YAG单晶中Ce离子掺杂浓度与封装的白光LED之间有对应关系,在650 nm红粉调节下Ce离子最佳掺杂浓度范围为0.034~0.066.     

YAG∶Ce体系中稀土离子掺杂对Ce3+的光谱性能的影响

采用高温固相法合成了一系列的(Y0.95Ln0.01Ce0.04)3Al5O12(简称YAG∶Ce,Ln), 系统地研究了此体系中的Ln3+对Ce3+的发光强度的影响. 结果表明, 在YAG∶Ce的体系中, La3+, Gd3+, Lu3+等光学透明离子的少量掺杂对Ce3+的发光强度的影响不大; 掺入少量的Pr3+, Sm3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+等稀土离子, 由于它们的能级与Ce3+的能级有交叠, 使它们之间存在着竞争吸收或能量转移, 对Ce3+的发光有较明显的变化, 其中, Pr3+和Sm3+的掺入使其在红光区有发射峰, 可以增加YAG∶Ce的红色成分以提高显色性; Nd3+, Eu3+和Yb3+对Ce3+的发光有严重的猝灭作用.     

Doping Effect of Bi~(3+) on the Properties of YAG:Ce~(3+),Mn~(2+) Phosphor Ceramics for Warm WLEDs

A series of Bi³⁺-doped YAG:Ce³⁺, Mn²⁺ ceramics was synthesized successfully by gel-casting method and structurally characterized by XRD and SEM. The doping effect and related mechanism of Bi³⁺ upon the luminescent property were studied. It can be assigned to the energy transfer of multipolar interaction from Bi³⁺ to Ce³⁺, leading to the improvement of emission intensity about 58% for 0.0001 Bi³⁺ and 0.05 Mn²⁺ doping. In addition, the emission is significantly red-shifted with the peak at 590 nm for the Y2.9939 Ce0.006 Bi0.0001 Al4.96 Mn0.02 Si0.02 O12 ceramic specimen with in-line transmittance 81.6% at 1100 nm. The LED module assembled from Y2.9939 Ce0.006 Bi0.0001 Al4.96 Mn0.02 Si0.02 O12 ceramic owns correlated color temperature(CCT) of 3960 K and luminous efficiency(LE) of 92 lm/W, implying that doping Bi³⁺ shows a good sensitization effect in the YAG:Ce³⁺, Mn²⁺ ceramic system and further serving as an attracting phosphor candidates for warm WLEDs applications.     

白光LED用Ce∶YAG单晶的光学性能与掺杂浓度分析

采用提拉法生长Ce∶YAG单晶, 通过X射线衍射和激发发射光谱对其晶相结构和光谱特性进行了表征, 研究了Ce∶YAG单晶封装白光LED的最佳掺杂浓度. 在455 nm蓝光激发下, Ce∶YAG单晶的发射光谱可由中心波长526 nm(5d¹²E_gГ_8g→4f ¹²F_7/2Г_8u)的宽发射带(500~650 nm)组成; 激发光谱由343 nm(4f ¹²F_5/2Г_7u→5d^{1 2}E_gГ_7g)和466 nm(4f ¹²F_5/2Г_7u→5d^{1 2}E_gГ_8g)2个激发峰组成; Stokes位移为2448 cm^-1, Huang-Rhys因子为6.12. 研究结果表明, Ce∶YAG单晶中Ce离子掺杂浓度与封装的白光LED之间有对应关系, 在650 nm红粉调节下Ce离子最佳掺杂浓度范围为0.034~0.066.     

溶胶凝胶法制备Y_2O_3∶Eu发光薄膜

以无机盐为水解原料,用溶胶 凝胶法制备了透明、稳定的前驱液,加入适量的成膜物质聚乙烯醇后,用浸渍拉提法在石英玻璃表面得到均匀的溶胶膜,经过室温干燥和低温处理的薄膜再于一定的温度下烧结,得到了红光发射掺铕的氧化钇薄膜.通过X射线衍射对膜的结构进行表征,表明在600℃时就开始了晶化,在900℃时形成单相Y2O3晶体.激发光谱和发射光谱显示,在220nm和260nm之间有很宽的激发峰,最强峰在236nm处,而发射主峰在614nm处,是一种很好的红光发射薄膜材料.     

Luminescence investigation on ultraviolet-emitting rare-earth-doped phosphors using synchrotron radiation

Three series of new ultraviolet-emitting Ca(9)Y(PO(4))(7):Ln(3+) (Ln = Ce, Gd, Pr) phosphors were synthesized, and their luminescence was investigated. Under vacuum ultraviolet excitation Ca(9)Y(PO(4))(7):Ce(3+) phosphors emit UVA light with one broad emission centered at 346 nm, on account of the 5d(1) → 4f(1) transition of Ce(3+) ions; the optimal doping concentration of these phosphors is 0.2 mol. Ca(9)Y(PO(4))(7):Gd(3+) phosphors show a strong 4f(7) → 4f(7) transition and a sharp UVB emission band at 312 nm; the optimal doping concentration of these phosphors is 0.7 mol. The PL spectra of Ca(9)Y(PO(4))(7):Pr(3+) show two broad UVC emission bands centered between 230 and 340 nm, owing to the 4f(1)5d(1) → 4f(2) transition of Pr(3+) ions; the optimal doping concentration of these phosphors is 0.2 mol. Under 172 nm excitation, we found that the luminescence intensity of the UVA-emitting Ca(9)Y(PO(4))(7):0.2Ce(3+) is 0.3675 times that of BaSi(2)O(5):0.05Pb(2+), that of the UVB-emitting Ca(9)Y(PO(4))(7):0.7Gd(3+) is 1.7 times that of YAl(3)(BO(3))(4):0.25Gd(3+), and that of the UVC-emitting Ca(9)Y(PO(4))(7):0.2Pr(3+) is 1.5 times that of LaPO(4):0.1Pr(3+). The thermal stability investigation indicated that the luminescence decay was only 9.2%, 18.2%, and 10.3% for Ca(9)Y(PO(4))(7):0.2Ce(3+), Ca(9)Y(PO(4))(7):0.7Gd(3+), and Ca(9)Y(PO(4))(7):0.2Pr(3+) at 250 °C relative to that at ambient temperature, respectively. The Ca(9)Y(PO(4))(7):Ln(3+) (Ln = Ce, Gd, Pr) phosphors exhibit high emission efficiency and excellent thermal stability.     

Effects of nano-YAG (Y3Al5O12) crystallization on the structure and photoluminescence properties of Nd3+-doped K2O–SiO2–Y2O3–Al2O3 glasses

Nd³⁺-doped precursor glass in the K₂O–SiO₂–Y₂O₃–Al₂O₃ (KSYA) system was prepared by the melt-quench technique. The transparent Y₃Al₅O₁₂ (YAG) glass–ceramics were derived from this glass by a controlled crystallization process at 750 °C for 5–100 h. The formation of YAG crystal phase, size and morphology with progress of heat-treatment was examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Fourier transformed infrared reflectance spectroscopy (FT-IRRS). The crystallite sizes obtained from XRD are found to increase with heat-treatment time and vary in the range 25–40 nm. The measured photoluminescence spectra have exhibited emission transitions of ⁴F_3/2 → ⁴I_J (J = 9/2, 11/2 and 13/2) from Nd³⁺ ions upon excitation at 829 nm. It is observed that the photoluminescence intensity and excited state lifetime of Nd³⁺ ions decrease with increase in heat-treatment time. The present study indicates that the incorporation of Nd³⁺ ions into YAG crystal lattice enhance the fluorescence performance of the glass–ceramic nanocomposites.     

Study on optical properties of rare-earth ions in nanocrystalline monoclinic SrAl2O4: Ln (Ln = Ce3+, Pr3+, Tb3+)

SrAl(2)O(4): Ln (Ln = Ce(3+), Pr(3+), Tb(3+)) nanocrystals have been synthesized by the combustion method. The results of XRD indicated that the resulting SrAl(2)O(4): Ln (Ln = Ce(3+), Pr(3+), Tb(3+)) nanocrystals have a reduced and distorted monoclinic lattice compared with bulk materials. The spectral properties are measured, and it is found that the excitation peaks of 5d energy levels red shift in nanocrystals in contrast to that in bulk crystals. The mechanism of spectra and energy changes is investigated. The order of the degree of red shift for nano SrAl(2)O(4): Ln (Ln = Ce(3+), Pr(3+), Tb(3+)) crystals is Pr(3+) > Ce(3+) > Tb(3+), which is in good agreement with our predicted results.     

KZnF3∶Ce，Tb的溶剂热合成及光谱性质

采用溶剂热法合成了Ce3+,Tb3+单掺和双掺KZnF3发光粉。分析了样品的结构与形貌。结果表明,所合成的样品均为单相,颗粒粒度分布均匀。讨论了它们的光谱特性。研究发现,在KZnF3∶Ce3+激发光谱中激发带劈裂成2个带峰,最大发光中心分别位于263 nm(主峰)和246 nm,而在发射光谱中只观察到1个带状发射峰,最大发射中心位于330 nm。在KZnF3∶Tb3+激发光谱中存在较强的基质激发峰,而在发射光谱中,发现Tb3+的5D4→7FJ(J=6,5,4,3)跃迁。在KZnF3双掺体系中,Tb3+的发光强度随Ce3+的浓度增加而增强,存在Ce3+→Tb3+能量传递,尤其是Tb3+的5D4→7F5跃迁发射显著增强,有望成为一种有发展前途的绿色荧光材料。     

Electrospinning synthesis and luminescence properties of one-dimensional La(9.33)(SiO4)6O2: Ln3+ (Ln = Ce, Eu, Tb) microfibers

One-dimensional La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) microfibers were fabricated by a simple and cost-effective electrospinning method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and low voltage cathodoluminescence (CL) as well as kinetic decay were used to characterize the resulting samples. SEM and TEM results indicated that the diameter of the microfibers annealed at 1000 °C for 3 h was 200-245 nm. The microfibers were further composed of fine and closely linked nanoparticles. La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) phosphors showed the characteristic emission of Ce(3+) (5d → 4f), Eu(3+) ((5)D(0)→(7)F(J)) and Tb(3+) ((5)D(3,4)→(7)F(J)) under ultraviolet excitation and low-voltage electron beams (3-5 kV) excitation. An energy transfer from Ce(3+) to Tb(3+) was observed in the La(9.33)(SiO(4))(6)O(2): Ce(3+), Tb(3+) phosphor under ultraviolet excitation and low-voltage electron beam excitation. Luminescence mechanisms were proposed to explain the observed phenomena. Blue, red and green emission can be realized in La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) microfibers by changing the doping ions. So the La(9.33)(SiO(4))(6)O(2): Ln(3+) (Ln = Ce, Eu, Tb) phosphors have potential applications in full-color field emission displays.