用于白光LED的高亮度蓝白色荧光粉Ca2SiO3Cl2：Eu2+的发光性质

采用固相法在较低温度下合成了Eu²⁺激活的Ca₂SiO₃Cl₂高亮度蓝白色发光材料,并对其发光性质进行了研究。其发射光谱由两个谱带组成,峰值分别位于420,498nm处,归结为Ca₂SiO₃Cl₂晶体中占据两种不同Ca²⁺格位的Eu²⁺离子的5d→4f跃迁发射。改变Eu²⁺浓度,可以使样品的发光在蓝白色和绿白色之间变化。当Eu²⁺浓度为0.005mol^-1时,样品呈现很亮的蓝白色发光。两个发射峰的激发光谱均分布在250~410nm的波长范围内,峰值分别位于333,369nm处。Ca₂SiO₃Cl₂:Eu²⁺可被InGaN管芯产生的近紫外辐射有效激发,是一种性能良好的白光LED用单一基质蓝白色荧光粉。     

白光LEDs用Ca9.15La0.9(PO4)7∶Eu2+,Mn2+材料的发光特性及能量传递(英文)

利用高温固相法合成了Ca_9.15La_0.9(PO₄)₇∶0.05Eu²⁺,yMn²⁺和Ca_9.3La_0.8(PO₄)₇∶0.05Eu²⁺,yMn²⁺系列荧光粉。通过荧光粉的发射光谱和荧光衰减曲线证实Eu²⁺、Mn²⁺之间存在能量传递,且增大Mn²⁺的掺杂浓度,获得了从青光(绿光)到白光变化的荧光粉。材料的热稳定性显示Eu²⁺的两个不同颜色的发射峰表现出不同的温度猝灭行为。Ca_9.15La_0.9(PO₄)₇∶0.05Eu²⁺,0.35Mn²⁺的色坐标接近标准白光且色温与太阳光相近,光谱覆盖整个可见光区域。研究结果...     

SrAl2O4∶Eu2+,Dy3+长余辉发光材料的喷雾热解制备及其表征

采用喷雾热解两段法制备了SrAl₂O₄∶Eu²⁺ ,Dy³⁺长余辉发光材料,并利用XRD、SEM、荧光长余辉亮度测试等方法分析了不同制备工艺条件下SrAl₂O₄∶Eu²⁺ ,Dy³⁺发光材料的结构、形貌以及发光性能的变化。结果表明:采用喷雾热解两段法可制备出球形SrAl₂O₄∶Eu²⁺ ,Dy³⁺长余辉发光材料,SrAl₂O₄∶Eu²⁺ ,Dy³⁺的晶体结构与α-SrAl₂O₄磷石英晶体结构相同。热解温度、还原温度、添加剂对产物的形貌、粒度分布、发光性能有较大影响。较之高温固相法,喷雾热解法制备的SrAl₂O₄∶Eu²⁺ ,Dy³⁺具有发光性能好、形貌好、粒度分布窄等优点。     

Sr2+掺杂荧光粉Ca2Nb2O7：Eu3+的发光特性

采用高温固相法制备出Ca_1.97-xSr_xNb₂O₇：3%Eu³⁺（x=0.10,0.50,1.0,1.5,1.97）红色荧光粉,研究了Ca_1.97-xSr_xNb₂O₇：3%Eu³⁺的发光特性及Sr²⁺的浓度对该荧光粉发光性质的影响。随着Sr²⁺浓度的改变,Ca_2-xSr_xNb₂O₇：Eu³⁺的XRD呈现不同的相。Ca_1.97Nb₂O₇：3%Eu³⁺（x=0）的激发光谱中,302 nm附近的强宽带来自于O^2-→Eu³⁺电荷转移跃迁,272 nm附近的肩峰来自于NbO^7-₆基团的电荷转移跃迁,350~600 nm范围内的锐锋属于Eu³⁺的特征4f-4f组内跃迁。在398 nm激发下,发射光谱的最强峰位于616 nm,属于Eu³⁺的⁵D₀→⁷F₂电偶极跃迁,发射出强烈的红光。当Ca²⁺逐渐被Sr²⁺取代时,Ca_2-xSr_xNb₂O₇：Eu³⁺的各激发峰的强度先提高后降低,且O^2-→Eu³⁺电荷转移跃迁发生明显红移。少量Sr²⁺的掺杂可以有效提高Ca_2-xSr_xNb₂O₇：Eu³⁺ 的红光发射强度,当x=0.01时该荧光粉的红光发射达到最强,可以被紫外LED芯片激发。     

双掺Eu3+ 和Tb3+ 的下转换β-NaYF4的合成与发光性能

采用高温溶剂热法合成了下转换发光材料NaYF₄∶Eu³⁺ 和NaYF₄∶Eu³⁺,Tb³⁺ ,采用X射线衍射(XRD)、场发射扫描电镜(FESEM)、激发(PLE)谱和光致发光(PL)谱对材料的物相结构、形貌特征和发光性质进行了表征和研究,并分析了其发光原理。结果表明:所合成的NaYF₄∶Eu³⁺ 和NaYF₄∶Eu³⁺,Tb³⁺ 为纯六方相晶体,尺寸在100 nm左右;改变Eu³⁺ 和Tb³⁺ 的掺杂浓度后晶格结构没有发生明显变化,说明Eu³⁺ 和Tb³⁺ 取代的是Y³⁺的晶格位置;在394 nm光的激发下,检测到Eu³⁺ 在⁵D₀→⁷F₁ 和⁵D₀→⁷F₂跃迁处的特征发射光,并且可见光强度随着Eu³⁺ 离子掺杂浓度的变化而变化。另外Tb³⁺ 离子浓度对NaYF₄∶Eu³⁺ 晶体结构产生了一定的影响,说明掺杂Tb³⁺ 离子改变了Eu³⁺ 离子所处的配位环境,导致红色发光带增强,而这主要源于电偶极子跃迁的贡献。     

Ca2Li2BiV3O12∶Eu3+荧光粉的制备和发光性能

采用高温固相法成功合成了一种可用于白光LED的Ca₂Li₂BiV₃O₁₂∶Eu³⁺新型红色荧光粉,使用X射线衍射仪和荧光分光光度计对合成样品进行了表征,研究了合成温度和Eu³⁺含量对合成样品相组成和发光性能的影响。结果表明,采用高温固相法在650~700 ℃能合成纯度较高、结晶度好的Ca₂Li₂BiV₃O₁₂∶Eu³⁺荧光粉,合成样品激发带覆盖200~400 nm,发射光谱的线状发射峰可归属于Eu³⁺的⁵D₀→⁷F_J(J= 1, 2, 3,4)特征锐线发射,Eu³⁺摩尔分数为14%时荧光粉的发光强度最大。     

Bi3+、Eu3+共掺杂La4GeO8荧光粉的制备及可调发光

为了开发出高效稳定的单一基质白光发射荧光材料,本工作通过高温固相法成功合成了一系列La₄GeO₈∶Bi³⁺,Eu³⁺荧光粉样品,并通过X射线衍射、室温光谱、变温光谱等手段研究了实验样品的结构与发光性能。研究发现,Bi³⁺离子在该结构中占据两种不同的格位(Bi³⁺(Ⅰ)和Bi³⁺(Ⅱ)),且在紫外光激发下呈现两个峰值分别在475 nm和620 nm的宽带发射。对于Bi³⁺、Eu³⁺共掺样品,由于Bi³⁺(Ⅰ)与Eu³⁺之间的竞争吸收、Bi³⁺(Ⅰ)至Bi³⁺(Ⅱ)以及Bi³⁺(Ⅱ)至Eu³⁺的能量传递作用,可实现蓝色至红色、橙红色至红色的可调发光。特别地,样品La₄GeO₈∶0.07Bi³⁺,0.0...     

激发波长和Eu2+的掺杂量对Sr4Al14O25 ∶ Eu2+ , Dy3+发光性能的影响

采用溶胶-凝胶法在低温、还原气氛下制备了长余辉发光材料Sr₄Al₁₄O₂₅ ∶ Eu²⁺,Dy³⁺。用X射线粉末晶衍射对其进行了物相鉴定,表明在1 200 ℃已经得到纯相的Sr₄Al₁₄O₂₅ 产物。研究了铕和锶的比值、激发光波长对所制备的Sr₄Al₁₄O₂₅ ∶ Eu²⁺, Dy³⁺发光性能的影响并对其影响机理进行了探讨。样品的发光性能测试结果表明:采用溶胶-凝胶法制备长余辉发光材料Sr₄Al₁₄O₂₅ ∶ Eu²⁺, Dy³⁺,其灼烧温度比高温固相法灼烧温度低;激发光谱向长波方向延伸时,在488 nm处发射峰增强,在410 nm处发射峰减弱;在一定范围内发光强度随着Eu²⁺量的增加而增强,Eu²⁺的最佳掺杂量为0.007, Eu²⁺的掺杂量超过0.007时会发生浓度猝灭。     

Eu2+在Ba2Ca(BO3)2中的发光特性及浓度猝灭

采用高温固相法,以CaCO₃ (A.R)、BaCO₃ (A.R)、H₃BO₃ (A.R)和Eu₂O₃ (99.99%)为原料制备了Ba₂Ca(BO₃)₂∶Eu²⁺绿色发光材料,测量了材料的晶体结构、发光特性及色坐标等。Ba₂Ca(BO₃)₂∶Eu²⁺材料的激发光谱覆盖200~500 nm的紫外-可见光区。在400 nm近紫外光激发下,材料的发射光谱为一主峰位于537 nm的非对称宽谱,对应于Eu²⁺的4f⁶5d¹→4f⁷特征跃迁。研究发现,随Eu²⁺掺杂浓度的增大,Ba₂Ca-(BO₃)₂∶Eu²⁺材料的发射强度呈现先增大、后减小的变化趋势,最大发射强度对应的Eu²⁺掺杂摩尔分数为2%。造成发射强度下降的原因为浓度猝灭,其机理为电偶极-电偶极相互作用。依据晶格常数及实验光谱数据,得出临界距离R_c分别为2.64 nm和2.11 nm。随Eu²⁺掺杂浓度的增大,Ba₂Ca(BO₃)₂∶Eu²⁺材料的色坐标变化微小。计算得到Ba₂Ca(BO₃)₂∶2%Eu²⁺的转换效率约为72%。     

氧空位对Eu2+, Dy3+掺杂的Ca5MgSi3O12发光及余辉性能的影响

利用高温固相法合成了稀土离子Eu²⁺, Dy³⁺掺杂的Ca₅MgSi₃O₁₂长余辉发光材料. 利用光谱学证明了在材料内部存在与氧空位有关的缺陷发光. 通过对比不同条件下合成样品的发光及余辉性能, 发现氧空位对材料的发光及余辉均起到促进作用. 同时发现氧空位发光可以向发光中心传递能量. 利用热释光曲线系统的分析了氧空位对余辉性能的影响. Ca₅MgSi₃O₁₂:Eu²⁺,Dy³⁺是一种潜在的长余辉发光材料. 关键词： 长余辉 氧空位 能量传递 热释光     

The electronic structure and photoluminescence properties of Ca2GeO4:Eu in ultraviolet and vacuum ultraviolet region

Ca₂GeO₄:Eu³⁺ phosphors were synthesized by the solid state method. The ultraviolet and vacuum ultraviolet excited photoluminescence properties were investigated in detail. It revealed that the emission of Ca₂GeO₄:Eu³⁺ comprised two parts: the red emission of Eu³⁺ and host defect emission in 330-550 nm. Ca₂GeO₄:Eu³⁺ presented intense excitation intensity at 163-200 and 466 nm, which suggested the potential applications in plasma display panels and light emitting diodes. The excitation spectra were studied to identify the photoluminescence mechanisms of Ca₂GeO₄:Eu³⁺. First principles calculation within the local density approximation of the density functional theory was applied to calculate the electronic structure and linear optical properties of Ca₂GeO₄.     

Eu2+激活的Ca3SiO5绿色荧光粉的制备和发光特性研究

研究了Eu²⁺激活的绿色发光材料Ca₃SiO₅的制备条件和发光性质. Eu²⁺中心形成主峰值为501 nm和次峰值为570 nm的特征宽带，两峰值叠加形成发射峰值为502nm的绿色发射光谱带. 利用这些光谱结果和Van Uitert 经验公式，确认Ca₃SiO₅:Eu²⁺中存在两种性质有差异的Eu²⁺发光中心，它们分别占据基质中八配位的Ca²⁺(Ⅰ)格位和四配位的Ca²⁺(Ⅱ)格位. 其激发光谱分布在250—450 nm的波长范围，峰值位于375 nm处，可以被InGaN管芯产生的350—410 nm辐射有效激发. 关键词： 发光 荧光粉 绿色荧光粉 3SiO₅')" href="#">Ca₃SiO₅ 2+')" href="#">Eu²⁺     

A promising red-emitting phosphor for white-light-emitting diodes prepared by a modified solid-state reaction

Using urea, boric acid and polyethylene glycol (PEG) as auxiliary reagents, the novel red-emitting phosphors Ca₁₉Zn₂ (PO₄)₁₄:Eu³⁺ have been successfully synthesized by a modified solid-state reaction. Thermogravimetric (TG) analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) spectra were used to characterize the resulting phosphors. The dependence of the photoluminescence properties of Ca₁₉Zn₂ (PO₄)₁₄:Eu³⁺ phosphors upon urea, boric acid and PEG concentration and the quadric-sintered temperature were investigated. Luminescent measurements showed that the phosphors can be efficiently excited by ultraviolet (UV) to visible region, emitting a red light with a peak wavelength of 616 nm. The material has potential application as a fluorescent material for ultraviolet light-emitting diodes (UV-LEDs).     

Luminescent properties of Li2 (Ca0.99, Eu0.01) SiO4: B3+ particles as a potential bluish green phosphor for ultraviolet light-emitting diodes

In our study, the 1% mol Eu²⁺ doped Li₂CaSiO₄: B³⁺ phosphors were prepared by the combustion method as fluorescent material for ultraviolet, light-emitting diodes (UV-LEDs) used as a light source. The properties of Li₂ (Ca_0.99, Eu_0.01) SiO₄: B³⁺ phosphors with urea concentration, doping boric acid and a series of initiating combustion temperature were investigated. The crystallization and particle sizes of Li₂ (Ca_0.99, Eu_0.01) SiO₄: B³⁺ has been investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Luminescence measurements showed that the phosphors can be efficiently excited by UV to the visible region, and exhibited bluish green light with a peak of 480 nm. The results showed that the boric acid was effective in improving the luminescence intensity of Li₂ (Ca_0.99, Eu_0.01) SiO₄: B³⁺ and the optimum molar ratio of boric acid to calcium nitrate was about 0.06. The optimized phosphors Li₂ (Ca_0.99, Eu_0.01) SiO₄: B _0.06 ³⁺ showed 180% improved emission intensity compared with that of the Li₂ (Ca_0.99, Eu_0.01) SiO₄ phosphors under ultraviolet (λ_ex =287 nm) excitation.      

Influence of phase and morphology on thermal conductivity of alumina particle/silicone rubber composites

Eu²⁺- and Eu³⁺-Zn₂GeO₄ were prepared by the high temperature solid-state reaction method. The phase purity and crystallinity of Zn₂GeO₄:Eu samples were characterized by X-ray diffraction (XRD). The excitation spectra, the emission spectra and the luminescence decay curves of the Eu²⁺- and Eu³⁺-Zn₂GeO₄ were investigated. Zn₂GeO₄:Eu²⁺ gives a bluish-green luminescence with one emission band located at 467 nm, and Zn₂GeO₄:Eu³⁺ presents an reddish-orange color due to the transition (⁵D₀→⁷F_J, J = 1 and 2) of the Eu³⁺ ions. The luminescence decay curves of Eu²⁺ and Eu³⁺ provide complementary evidence to the mixed valence of europium (Eu²⁺, Eu³⁺) in Zn₂GeO₄ host. These indicate that the mixed valence of europium (Eu²⁺, Eu³⁺) coexists in Zn₂GeO₄ host prepared in an oxidizing atmosphere. The abnormal reduction phenomenon of Eu³⁺→Eu²⁺ in Zn₂GeO₄ host prepared in an oxidizing atmosphere was reported and discussed on the basis of the charge compensation model.     

A novel red-emitting phosphor Ca9Bi(PO4)7:Eu3+ for near ultraviolet white light-emitting diodes

Red phosphors Ca₉Bi_1-x(PO₄)₇:xEu³⁺ (x = 0.06, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80 and 1.00) were synthesized by a conventional solid-state reaction (SSR) route. The X-ray diffraction patterns, photoluminescence spectra, ultraviolet–visible reflection spectroscopy, decay time and the International Commission on Illumination (CIE) chromaticity coordinates of these compounds were characterized and analyzed. The Eu-doped Ca₉Bi(PO₄)₇ phosphors exhibited strong red luminescence which peaks located at 615 nm due to the ⁵D₀→⁷F₂ electric dipole transition of Eu³⁺ ions after excitation at 393 nm. Ultraviolet–visible spectra indicated that the band-gap of Ca₉Bi_0.30(PO₄)₇:0.70Eu³⁺ is larger than that of Ca₉Bi(PO₄)₇. The results indicate that the phosphor Ca₉Bi_0.30(PO₄)₇:0.70Eu³⁺ can be a suitable red-emitting phosphor candidate for LEDs.     

Radiative properties of Eu in BaGa2S4

A photoluminescence study of the blue-green emitting BaGa₂S₄:Eu²⁺ phosphor is reported. Diffuse reflectance, excitation and emission spectra were examined with the aim to enlarge the fundamental knowledge about the emission of the Eu²⁺ rare earth ion in this lattice. The thermal dependence of the radiative properties and the influence of the Eu²⁺ concentration were investigated. The Stokes shift, the crystal field splitting and the activation energy of the thermal quenching were determined. By combining these results with data available in literature, we discussed the radiative properties of the BaAl₂S₄:Eu²⁺ blue phosphor in relation with those determined in this study for the isostructural BaGa₂S₄:Eu²⁺ phosphor.     

Combustion synthesis and luminescent properties of a new material Li2(Ba0.99,Eu0.01)SiO4:B for ultraviolet light emitting diodes

Using urea as fuel and boric as flux, a novel bluish green emitting phosphor Li₂(Ba_0.99,Eu_0.01)SiO₄:B³⁺ has been successfully synthesized using a combustion method. The material has potential application as the fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). The dependence of the properties of Li₂(Ba_0.99,Eu_0.01)SiO₄:B³⁺ phosphors upon urea concentration, boric acid doping and initiating combustion temperature were investigated. The crystallization and particle sizes of Li₂(Ba_0.99,Eu_0.01)SiO₄:B³⁺ have been investigated by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Luminescence measurements showed that the phosphors can be efficiently excited by ultraviolet (UV) to visible region, emitting a bluish green light with peak wavelength of 490 nm. The results showed that the boric acid was effective in improving the luminescence intensity of Li₂(Ba_0.99,Eu_0.01)SiO₄ and the optimum molar ratio of boric acid to barium nitrate was about 0.06. The optimized phosphors Li₂(Ba_0.99,Eu_0.01)SiO₄:B_0.06³⁺ showed 160% improved emission intensity compared with that of the Li₂(Ba_0.99,Eu_0.01)SiO₄ phosphors under UV (λ_ex=350 nm) excitation.     

Photoluminescence properties and energy transfer of Ca3WO6:Sm3+ co-doped Eu3+

A reddish-orange phosphor, Ca₃WO₆:Sm³⁺, was synthesized by the convenient solid-state reaction method and characterized by X-ray diffraction (XRD). Photoluminescence properties and concentration quenching of Ca₃WO₆:Sm³⁺ phosphor have been discussed in the excitation and emission spectra. Ca₃WO₆:Sm³⁺ phosphor is able to generate a strong excitation peak, which matches the emission wavelength from near-UV LEDs. Energy transfer from Sm³⁺ to Eu³⁺ in Ca₃WO₆ host is observed and investigated in detail. The chromaticity coordinates of Ca₃WO₆:Sm³⁺ can be regulated to approach the NTSC standard values of red phosphor by codoping Eu³⁺ ions. The photoluminescence properties suggest that novel Ca₃WO₆:Sm³⁺, Eu³⁺ phosphor might have a potential application for near-UV LEDs.     

Luminescent properties of a new green emitting Eu doped CaZrSi2O7 phosphor for WLED applications

CaZrSi₂O₇ (CZS), a modification of the thortveitite family, was prepared as a polycrystalline powder material by the conventional solid-state reaction method. Structural, thermal and photoluminescence (PL) properties of the prepared material were investigated in order to evaluate its potentiality. XRD patterns confirm the monoclinic phase of CaZrSi₂O₇: Eu²⁺ phosphors.. Emissions arising from transitions between the 5d and 4f orbital gaps of Eu²⁺ are manifested in the broadband excitation and emission spectra with major peaks at 363 and 512 nm, respectively. The excitation wavelength matches well with that of the emission of the ultraviolet-light emitting diode (UV-LED). Concentration quenching occurs when the Eu²⁺ concentration is beyond 0.05 and the dipole-dipole interaction was the reason for the corresponding quenching mechanism. The temperature dependence of emission intensity of CZS: Eu²⁺ phosphor was investigated and it showed better thermal stability than the standard YAG: Ce³⁺ phosphor.