溶胶-凝胶法合成Y_3Al_5O_(12):Ce~(3 ),Tb~(3 )稀土荧光粉的研究

采用溶胶－凝胶法在低温下合成了 Ｙ３Ａｌ５Ｏ１２：０．０８Ｃｅ３＋; ０．１２Ｔｂ３＋稀土荧光粉．通过 Ｘ射线衍射（ＸＲＤ）分析及激发、发射光谱测试结果表明：合成的粉末为ＹＡＧ晶体结构,粉体 的最大激发峰为２７３ｎｍ,最大发射峰为５４５ｎｍ,色坐标为：ｘ＝０．３３１;ｙ＝０．５５８,在２７３ｎｍ的紫 外光激发下发出明亮的绿光．     

Ce^3＋,Tb^3＋在Al4B2O9和Al18B4O33基质中的发光

采用固相反应法在Ａｌ２Ｏ３－Ｂ２Ｏ３体系中合成了Ａｌ４Ｂ２Ｏ９和Ａｌ１８Ｂ４Ｏ３３两个相关化合物，测定了在两种基质中Ｃｅ３＋，Ｔｂ３＋和Ｃｅ３＋－Ｔｂ３＋的光谱，观察到在两种基质中Ｃｅ３＋的光谱相似，Ｃｅ３＋的发射峰位置在Ａｌ１８Ｂ４Ｏ３３中比Ａｌ４Ｂ２Ｏ９稍有红移。实验表明，Ａｌ１８Ｂ４Ｏ３３将是一种好的发光基质     

Eu2+在多铝酸钠体系中的发光

应用高温固相法合成了Ｎａ的多铝酸盐,并研究了Ｅｕ＾２＋在体系中的发光性能,结果表明,Ｎａ１＋ｘＭｇＡｌ１１－ｘＯ１７体系在整个组成范围内保持Ｎａ的β－Ａｌ２Ｏ３结构不变,而对于Ｎａ１．６７－２ｘＢａｘＡｌ１０．３３Ｏ１７体系,在ｘ＝０．３０附近体系结构发生转变,ｘ〈０．３０,体系形成Ｎ的β－Ａｌ２Ｏ３结构的固溶体,ｘ〉０．３０,体系形成Ｂａ的β－Ａｌ２Ｏ３结构的有序体;与体系组成的和结构的变化相对     

PLZT（28／0／100）薄膜的溶胶－凝胶制备技术及显微结构

用溶胶—凝胶技术及回旋法，在石英玻璃和单晶ｓｉ基片上制备ＰＬＺＴ（２８／０／１００）多晶薄膜；在ＳｒＴｉＯ３和α－Ａ１２Ｏ３单晶基片上外延生长择优取向薄膜．其外延关系分别为（１００）ＰＬＺＴ（２８／０／１００）／／（１００）ＳｒＴｉＯ３和（１００）ＰＬＺＴ（２８／０／１００）／／（０００１）Ａｌ２Ｏ３．用ＩＲ，ＸＲＤ．ＲＨＥＥＤ，ＳＥＭ和ＳＩＭＳ分析凝胶中杂质、凝胶的分子结构和薄膜的显微结构．结果表明，用溶胶—凝胶技术能制备出显微结构良好的多组份陶瓷薄膜．     

纳米ZrO2/(1-n)SiO2-nAl2O3介孔复合作的制备与光致发光

采用溶胶－凝胶法和超临界干燥技术制备了（１－ｎ）ＳｉＯ２－ｎＡｌ２Ｏ３（ｎ＝０、０．０１、０．１）混合气凝胶体系，并以此作为载体，成功地将纳米ＺｒＯ２粒子组装到（１－ｎ）ＳｉＯ２－ｎＡｌ２Ｏ３介孔体系中，而形成纳米ＺｒＯ２／（１－ｎ）ＳｉＯ２－ｎＡｌ２Ｏ３介孔复合材料。光致发光光谱研究表明，室温下以３１６ｎｍ（３．９２ｅＶ）波长激发时，纳米ＺｒＯ２粒子５４０ｎｍ（２．３０ｅＶ）荧光峰，在介孔复合体     

BAS玻璃陶瓷的晶化行为与性能

用ＸＲＤ，ＤＴＡ，ＳＥＭ，ＴＥＭ和三点弯曲试验研究了溶胶－凝胶法合成的ＢＡＳ（ＢａＯ．Ａｌ２Ｏ３．２ＳｉＯ２）凝胶玻璃的结晶行为，晶型转变和热压ＢＡＳ的显微结构与性能，结果表明，ＢＡＳ凝胶玻璃法〉１０００℃时开始析晶，１１００℃时完全晶化，结晶相为六方钡长石，不加成核剂，呈现整体结晶特性，晶粒小于１μｍ加入５０ｍｇ．ｇ＾－１单斜钡长石作为晶种，可促进六方→单斜晶型转变，在１２５０℃处理７ｈ约有８０     

应用量子化学研究Ca_2Fe_（2-x）Al_xO_5的水化活性

用量子化学ＳＣＣ—ＤＶ—Ｘａ方法分析了Ｃａ_２Ｆｅ_（２-ｘ）ＡｌｘＯ_５体系中的Ｃａ_２Ｆｅ_２Ｏ_５（即Ｃ_２Ｆ），Ｃａ_２Ｆｅ_（１．４３）Ａｌ_（０．５７）Ｏ_５和Ｃａ_２Ｆｅ_（１．２８）Ａｌ_（０．７２）Ｏ５．认为它们的水化活性随Ａｌ的增加而提高的原因是：（１）Ａｌ的净电荷比Ｆｅ高，易吸收水分子的孤对电子；（２）Ａｌ-Ｏ键比Ｆｅ-Ｏ键弱，易断裂而容易与水反应．     

三价铈离子在氯硅酸镁钙中的晶体学格位研究

首次合成了发射蓝紫光的Ｃｅ＾３＋激活的氯硅酸镁钙ＣａｇＭｇ（ＳｉＯ４）４Ｃｌ２：Ｃｅ＾３＋新荧光粉,利用Ｃｅ＾３＋的光谱结果和Ｖａｎ Ｕｉｔｅｒｔ经验公式,结合对ＣａｇＭｇ（ＳｉＯ４）４Ｃｌ２晶体的结构研究,判断出ＣａｇＭｇ（ＳｉＯ４）４Ｃｌ２：Ｃｅ＾３＋中存在两种性质稍有差异的Ｃｅ＾３＋发光中心,这两种发光中心均占据其质中八配位的钙格位。     

(Ca,Mg)-α-Sialon的致密化,形成特性和显微结构

利用热压工艺制备了组份为（Ｃａ,Ｍｇ）ｘＳｉ１２－３ｘＡｌ３ｘＯｘＮ１６－ｘ（ｘ＝０．３、０．６、１．０和１．４）的（Ｃａ,Ｍｇ）－α－Ｓｉａｌｏｎ。研究结果发现,当ｘ≥１．０时,材料的主晶相为α－Ｓｉａｌｏｎ和含Ｍｇ的ＡｌＮＡ多型体。多型体的含量随ｘ值的增加而变大。以复合添加剂取代单一添加剂,不仅改善了α－Ａｉａｌｏｎ的烧结性能,ＴＥＭ和ＥＤＡＸ的结果还进一步表明添加的Ｃａ＾＋＋离子进入α－Ｓｉ     

应用量子化学研究Ca2Fe2—xAl2O5的水化活性

用量子化学ＳＣＣ－ＤＶ－Ｘα方法分析了Ｃａ２Ｆｅ２－ｘＡｌｘＯ５体系听ａ２Ｆｅ２Ｏ５，Ｃａ２Ｆ３１．４３Ａｌ０．５７Ｏ５和Ｃａ２Ｆ３１．２８Ａｌ０．７２Ｏ５，认为它们的水化活性随Ａｌ的增加而提高的原因是：（１）Ａｌ的净电荷比Ｆｅ高，易吸收水分子的弧对电子；（２）Ａｌ－Ｏ键比Ｆｅ－Ｏ键弱，易断裂而容易与水反应。     

新型黄绿色发光材料Sr2MgSi3O9:Ce3+,Tb3+的合成及光谱分析

采用凝胶-燃烧法在活性炭弱还原气氛下成功合成了新型荧光粉Sr2MgSi3O9 :Tb3+、Sr2MgSi3O9:Ce3+,Tb3+,用X射线粉末衍射仪(XRD)、扫描电镜(SEM)、荧光分光光度计等对合成产物进行了分析和表征.结果表明,所合成的发光材料与Sr2MgSi2O7具有相似的晶体结构,同属四方晶系.样品一次颗粒近似球形,粒径在100nm左右.Sr2MgSi3O9:Tb3+的激发光谱为一位于249nm的宽带,发射光谱主要由473、491、547、585nm等一系列发射峰组成,其中473nm(5D3→<7F3)为主发射峰,547nm(5D4→7F5)为次发射峰;样品Sr1.955MgSi3O9:Tb3+0.04,Ce3+0.005的激发光谱由峰值分别位于249和335nm的双激发带组成,其中后者为主激发带.在335nm激发下,其发射光谱由两部分组成,其中400nm附近的带状发射对应于Ce3+的发射,而491、547、588nm处的发射峰归属为Tb3+的5+D4→7FJ(J=6,5,4)跃迁发射,最强峰位于547nm,对应Tb3+的5D4→7F5跃迁.此外,探讨了Ce3+掺杂量对样品发光亮度的影响,发现Ce3+可以把能量传递给Tb3+,对Tb3+起到敏化作用.     

Single-composition trichromatic white-emitting Ca4Y6(SiO4)6O: Ce3+/Mn2+/Tb3+ phosphor: luminescence and energy transfer

A series of Ca(4)Y(6)(SiO(4))(6)O (CYS): Ce(3+)/Mn(2+)/Tb(3+) oxyapatite phosphors were prepared via high-temperature solid-state reaction. Under UV excitation, there exist dual energy transfers (ET), i.e., Ce(3+)→Mn(2+) and Ce(3+)→Tb(3+) in the CYS: Ce(3+), Mn(2+), Tb(3+) system and their emitting colors can be adjusted from blue to orange-red via ET of Ce(3+)→Mn(2+) and from blue to green via ET of Ce(3+)→Tb(3+), respectively. Moreover, a wide-range-tunable white light emission with high quantum yields (13%-30%) were obtained by precisely controlling the contents of Ce(3+), Mn(2+) and Tb(3+) ions. On the other hand, the CL properties of CYS: Ce(3+), Mn(2+), Tb(3+) phosphors have been investigated in detail. The studied results indicate that the as-prepared CYS: Ce(3+), Mn(2+), Tb(3+) phosphors have good CL intensity and CIE color coordinate stability with a color-tunable emission crossing the whole white light region under low-voltage electron beam excitation. In general, the white light with varied hues has been obtained in Ce(3+), Mn(2+), and Tb(3+)-triactivated CYS phosphors by utilizing the principle of energy transfer and properly designed activator contents under UV (284, 358 nm) and low-voltage (1-5 kV) electron beam excitation, which make them as a potential single-composition trichromatic white-emitting phosphor.     

Luminescence and energy transfer characteristics of Ce3+- and Tb3+-codoped nanoporous 12CaO 7Al2O3 phosphors

The novel green-emitting phosphors of 12CaO 7Al2O3:Ce3+ , Tb3+ (C12A7:Ce3+, Tb3+) were synthesized by a solid-state reaction. Upon the excitation of Ce3+ at 350 nm, the C12A7:Ce3+, Tb3+ phosphor shows intense green emissions located at 543 nm assigning to 5D4-7F5 transitions of Tb3+ ions, and weak blue emissions centered at 434 nm due to the transitions of Ce3+ 5d-4f. The photoluminescence (PL) intensity of Ce3+ decrease with increasing Tb3+ concentration, indicating the effective energy transfer (ET) occurred from Ce3+ to Tb3+ in C12A7:Ce3+, Tb3+. The ET efficiency between Ce3+ and Tb3+ in the optimum composition reaches to 99%. Based on Dexter's ET theory, we have demonstrated that the efficient ET is a resonant type via dipole-dipole mechanism with an energy transfer critical distance of 4.02 A. Our results suggested that C12A7:Ce3+, Tb3+ phosphor would be a promising green-emitting phosphor for UV-converting white light-emitting diodes.     

La(BO3,PO4):Ce,Tb,Gd的发光研究

以BPO4和稀土氧化物为原料制备了铈、铽、钇共掺杂的硼磷酸镧绿色荧光粉,研究了基质中Gd^3 、Ce^3 、Tb^3 的发光特性及它们之间的相互作用。在该基质中存在Ce^3 →Gd^3 、Gd^3 →Tb^3 、Ce^3 →Tb^3 的能量传递;当钆加入到铈、铽共掺杂的硼磷酸镧基质中会导致铈离子的发射减弱,铽离子^5D4→^7F1的发射显著增强,而^5D3→^7F1的发射没有明显变化,故有利于提高荧光粉的发光强度和绿色发射纯度。用硼磷酸钆作基质比用硼磷酸镧更能提高荧光粉的发光强度、发光纯度以及发光色坐标x的值,所以La(BO3,PO4):Ce,Tb,Gd和Gd(BO3,PO4):Ce,Tb均是理想的绿色发射材料。     

Precipitation based synthesis and luminescence of Ln (Eu,Ce, Dy,Sm, Tb) activated BaCa2Si3O9-Walstromite cyclosilicate phosphors

A series of new phosphors of BaCa₂Si₃O₉:Ln³⁺, (Ln = Eu, Ce, Dy, Sm, Tb) were synthesized by precipitation based method. Good crystallinity was achieved after annealing the sample at 750 °C for 1 h in air. X-ray powder diffraction (XRD) result confirmed the formation of desired BaCa₂Si₃O₉ host. The photoluminescent excitation and emission properties of Ln³⁺, (Ln = Eu, Ce, Dy, Sm, Tb) activated BaCa₂Si₃O₉ were investigated in detail. The photoluminescence (PL) analysis of individual Ln³⁺, (Ln = Eu, Ce, Dy, Sm, Tb) activated BaCa₂Si₃O₉ phosphors exhibits interesting characteristic emission properties in their respective regions. From the measured emission spectra, Judd–Ofelt (J–O) intensity parameters (Ω₂, Ω₄, Ω₆) have been calculated and using these J–O parameters various radiative parameters such as radiative transition probabilities (A_rad), radiative lifetimes (τ_R), branching ratios (β_R) and relative quantum yield have been calculated for the studied ions.     

Study on luminescence behavior of BaAl12O19:Tb, Eu

BaAl12O19:Tb, Eu phosphors were prepared by sol-gel technique. The luminescence properties and the energy transfer between Eu2+ and Tb3+ were investigated. For BaAll2O19:Tb phosphor, the strongest excitation peak and emission peak produced from Tb3+ transition of 5D4-7F5 were at 240 nm and at 550 nm respectively, while the peak shape was narrow and peak intensity was large. The Eu2+ added in the BaAl12O19:Tb induced energy transfer to Tb3+ and different color luminescence from blue (400 nm) to green (570 nm) was obtained by changing the ratio of Tb3+/Eu2+ with excitation at 240 nm.     

(La,Ce,Tb)(PO_4,BO_3)绿粉的合成及发光研究

首次用磷酸硼和稀土氧化物为主要原料制备铈、铽共激活的硼磷酸盐绿色荧光粉 ,并对Ce3+-Tb3+的能量传递进行了研究 ,发现在该基质中Ce3+、Tb3+间的能量传递为电多极子相互作用的共振传递 ,能量传递效率可高达 90 %。还研究了助熔剂对荧光粉粒度和发光特性的影响 ,实验结果表明 ,加了助熔剂后所得样品的颗粒明显变大 ,在 2 54nm紫外激发下Tb3+发射大大增强 ,光的纯度也得到改善。对不同基质荧光粉的研究发现 ,用硼磷酸盐绿粉比用硼酸盐和磷酸盐绿粉更适合做三基色粉配料。     

Luminescent properties of rare earth ions in one-dimensional oxide nanowires

Rare-earth doped one-dimensional oxide nanowires including LaPO4, La2O3, and Gd2O3 were synthesized by the hydrothermal method. Their luminescent properties including local environments, electronic transitions, energy transfer, and frequency up-conversion luminescence processes were systematically studied. In LaPO4:Eu and La2O3:Eu nanowires, different symmetry sites of Eu3+ ions were identified, which obviously differed from those of the corresponding micrometer-sized particles. This was attributed to crystal field degeneration in the fringe along the length axis. In LaPO4:Eu nanowires, the electronic transition rate of 5D1-sigmaJ7FJ increased approximately 2 times over that of the zero-dimensional nanoparticles and micrometer-sized particles, which was related to the variation of dipole field induced by shape anisotropy. Considering the nonradiative relaxations, meanwhile, the luminescent quantum efficiency for 5D1-sigmaJ7FJ transitions of Eu3+ in nanowires increased 100% over that in nanoparticles and 20% over that in micrometer particles. In Gd2O3:Eu3+, LaPO4:Ce3+, and LaPO4:Tb3+ nanowires and micrometer-sized particles, the electronic transition rate of rare earths had only a little variation. In LaPO4:Ce3+/Tb3+ nanowires, the energy transfer rate of Ce3+--> Tb3+ decreased 3 times compared to that in micrometer rods. Despite this, the brightness for the 5D4-7F5 green emissions of Tb3+ increased several times due to decreased energy transfer from the excited states higher than 5D4 to some defect levels. In Gd2O3:Er3+/Yb3+ nanocrystals, as the shape varied from nanopapers to nanowires, the relative intensity of up-conversion luminescence of 2H(11/2)/4S(3/2)-4I(15/2) and 4F(9/2)-4I(15/2) to the infrared down-conversion luminescence of 4I(13/2)-4I(15/2) increased remarkably, indicating efficient up-conversion luminescence. Our present results indicate that rare-earth-doped oxide nanowires is a type of new and efficient phosphors.     

Improving the angular color uniformity and the lumen output for multi-chip white LED lamps by green Ce0.67Tb0.33MgAl11O19:Ce,Tb phosphor

In this paper, we propose and discuss how to enhance the color uniformity and the lumen output of multi-chip white LED lamps (MCW-LEDs). This can be done by combining the green Ce_0.67Tb_0.33MgAl₁₁O₁₉:Ce,Tb phosphor (CeTb) and phosphor compounding. We find that the proposed method can have a significant effect on MCW-LEDs performance. Through simulation results, it is confirmed that the color uniformity and the lumen output of MCW-LEDs with average correlated color temperatures of 7000 and 8500 K grow with the concentration of CeTb, while the color rendering ability decreases. With proper choice of CeTb concentration, good performance of MCW-LEDs can be obtained.     

Photoluminescence green in microspheres of CaWO4:Tb processed in conventional hydrothermal

Green-phosphor spherical microparticles (2–4 μm in diameter) of CaWO₄:Tb³⁺ (CWO:Tb) exhibiting excellent emission at 545 nm have been synthesized by a conventional hydrothermal process directly without further sintering treatment. X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence excitation and emission spectra and decay curve were used to characterize the CWO:Tb phosphors. Because 12 at.% CWO:Tb phosphor shows broad and strong absorption in UV region, exhibits intensive green emission under 254 nm excitation in comparison with the commercial green fluorescent lamp phosphor (LaPO₄:Ce,Tb), it is considered to be a new promising phosphor for fluorescent lamps application.