Ca2Y7.9（SiO4）6O2-0.5xFx:Eu0.1（3+,2+）荧光粉的合成和发光特性

采用高温固相反应法在弱还原气氛下制备了Ca2Y7.9(SiO4)6O2-0.5xFx:Eu(2+,3+)0.1(x=0～4)系列荧光粉。晶胞参数a,c和晶胞体积V均随着F-置换量的增加呈线性减小,晶胞参数a和c的变化率相近。荧光体中Eu2+和Eu3+共存,Eu2+3d5/2与Eu3+3d5/2电子结合能分别为1128.4和1136.3 eV,Eu2+的3d5/2与3d3/2的电子结合能差为28.4 eV。Eu2+和Eu3+的3d5/2态XPS峰面积比为6.9∶1。激发光谱由Eu3+的两个电荷迁移(CTS)带和f-f跃迁激发线组成,x=0,1的试样中出现了Eu2+的f-d跃迁强激发谱带。激发到Eu3+的电荷迁移态或激发Eu2+,除了来自Eu3+的5D0能级的发射之外,还观察到了5D1能级的强发射和5D2能级的弱发射,并且激发Eu2+时5D1→7F4发射强度超过5D0→7F2,没有出现Eu2+的明显发射,Eu2+对Eu3+发光起到很好的敏化作用。5DJ(J>0)高能级发射来自4f格位的Eu3+发光中心,Eu2+的敏化起关键作用。Eu3+在4f和6h两种格位的分布比为4∶6。     

Eu3+掺杂双钙钛矿Sr2CaMoO6橙红色荧光粉的结构特征及其发光性能

采用EDTA-柠檬酸联合配位法制备一系列组成的(Sr1-xEux)2CaMoO6橙红色荧光粉。通过X射线衍射、拉曼光谱、扫描电镜及荧光光谱研究不同Eu3+离子掺杂浓度下Sr2CaMoO6∶Eu3+荧光粉的晶体结构、掺杂位置、形貌及其光致发光性能。Rietveld全谱拟合结果表明:掺杂后样品为(Ca/Mo)O6八面体少量倾斜的空间群为P21/n的正交双钙钛矿结构,随着Eu3+离子共掺杂浓度的增加,样品的晶胞体积减小;Eu3+离子取代八面体间隙的Sr2+位置致使双钙钛矿的T2g(1)拉曼振动模发生蓝移;在近紫外区宽而强电荷迁移带和蓝光激发下,该荧光粉分别发射以Eu3+离子5D0-7F1磁偶极跃迁为主的橙光和以5D0-7F2电偶极跃迁为主的红光,组成为(Sr0.98Eu0.02)2CaMoO6的荧光粉具有最强的橙红光发射强度,是一种潜在的适用于近紫外LED芯片的光转换红光材料。     

白光LED用Sr_(0.955)Al_2Si_(2-x)Ti_xO_8∶Eu~(2+)荧光粉的晶体结构和光谱特性

由高温固相反应制得Sr0.955Al2Si2-xTixO8∶Eu2+(x=0~1.0)系列试样,研究了Ti4+置换Si4+对其晶体结构和光谱特性的影响。Ti4+以类质同相替代Si4+进入基质晶格中,形成了连续固溶体,其晶胞参数a,b,c,β和晶胞体积V随Ti4+置换量呈线性递增。Ti4+置换Si4+对晶胞参数c的影响显著,b其次,a最小。荧光激发谱为宽带,位于230~400nm,由267nm、305nm、350nm和375nm4个峰拟合成,表观峰值位于351nm;随着Ti4+置换量的增加,半高宽(FWHM)从105nm减小到93nm。发射光谱位于380~600nm,表观峰值位于407nm,可由406nm和441nm两峰拟合而成并且随Ti4+置换量增加线性红移,Ti4+进入晶格对长波长发射中心影响较少;Ti4+置换量为1.0时,表观发射峰位从407nm红移至417nm;利用试样荧光光谱和VanUitert经验公式,得出SrAl2Si2O8∶Eu2+中Sr2+的配位数为9。随着Ti4+置换量Si4+进入基质晶格,造成Eu-O距离变小,使得Eu2+所处的晶体场强度增强,发光中心Eu2+的5d能级分裂增大,造成Eu2+最低发射能级重心下移,两拟合谱峰峰位均呈线性红移。     

Sr2.975-xCaxAlO4F:Ce0.0253+荧光粉的制备及发光性能研究

采用高温固相法制备了Sr2.975-xCaxAlO4F:Ce30.+025(0≤x≤1.0)发光材料,通过X射线衍射、荧光光谱测试分析,研究了Ca2+掺杂对晶体结构和发光性能的影响。XRD测试表明Ca2+的掺入并没有改变基质晶格的结构类型,且在Sr3AlO4F基质中固溶极限不超过x=0.9。荧光光谱分析表明,Ca2+掺入后能有效提高发光强度,使激发光谱宽化和发射光谱红移,在Ca2+掺入量为x=0.4时发射强度最高。考察了Sr3-xCaxAlO4F:Ce3+(x=0,x=0.4)在不同Ce3+浓度的发射强度与峰值波长,发现Ca2+掺杂量由x=0增加至x=0.4时,对应的Ce3+的猝灭浓度由0.01降低至0.0025,并且Ce3+的猝灭机制为电偶极-电偶极相互作用。     

LnBaB_9O_(16)∶Eu~(3+)(Ln=La,Y)的结构与荧光性质

利用电子衍射、X射线衍射和荧光光谱等方法研究了 L n Ba B9O16(L n=L a,Y)的结构特性 .L n Ba B9O16为单斜晶系 ,其中 L a Ba B9O16的晶胞参数 a=1.36 6 0 nm,b=0 .7882 nm,c=1.6 2 53nm,β=10 6 .15°;YBa B9O16的晶胞参数 a=1.3476 nm,b=0 .7776 nm,c=1.6 0 4 0 nm,β=10 6 .38°.荧光光谱研究表明 ,这两种化合物结构不同 ,Y3 +在 YBa B9O16结构中处于中心对称格位 ,而 L a Ba B9O16中 L a3 +的格位则无中心对称性 .Gd3 +部分取代 L a Ba B9O16∶ Eu3 +中的 L a3 +可改善 Eu3 +离子的发光性质 .L a Ba B9O16∶ Eu3 +在真空紫外区的吸收比较弱 ,这可能与硼氧比较小有关 .     

LED用Sr(1-1.5x)Mo0.8Si0.2O3.8:Eu3+x红色荧光粉的制备及其荧光性能

通过高温固相法合成了LED用红色荧光粉Sr(1-1.5x)Mo0.8Si0.2O3.8∶Eu3+x（x=0.1,0.2,0.3,0.4,0.5）。 通过XRD、激发光谱和发射光谱测试了材料的物相组成以及发光性能。 x=0.1样品的XRD谱与JCPDS 08-0482(SrMoO4)的标准卡片相同。 Eu3+代替晶格中Sr2+的位置成为发光中心。 随着Eu3+含量x的增加,593 nm处的5D0-7F1跃迁和614 nm处的5D0-7F2跃迁发射强度会相互转换：当x≤0.4时,以磁偶极5D0-7F1跃迁为主,发射橙色光;而当x=0.5时,以电偶极5D0-7F2跃迁发射为主,发射红光。 可能是过量掺杂的Eu3+离子,只能存在于晶格空位形成缺陷,无法占据SrMoO4中Sr2+的格位中,Eu3+在晶格中占据非对称中心的格位,导致电偶极跃迁变成允许跃迁,从而增加了5D0-7F2跃迁,减弱了5D0-7F1跃迁。 因此,可以通过调节激活剂的含量获得不同发光色的荧光粉。 Eu3+掺杂的硅钼酸锶体系,614 nm激发下,在368 nm处出现宽的基质吸收峰和467 nm处7F0-5D2的跃迁峰,且这2处的吸收峰在x=0.5时比x=0.4时强3倍左右。 材料能非常好的吸收368 nm波长的光,产生颜色可调的橙红色。 与近紫外光LED芯片匹配良好。     

Sr~(2+(置换对Eu~(2+)掺杂钙长石晶体结构和光谱特性的影响

采用高温固相法在弱还原气氛下制备了Ca0.955-xSrxAl2Si2O8:Eu2+(x=0~0.9)系列荧光粉,研究了Sr2+置换Ca2+对晶体结构和光谱特性的影响。Sr2+进入CaAl2Si2O8晶格与Ca2+发生类质同相替代形成连续固溶体,物相从CaAl2Si2O8相(Triclinic,P1)逐渐转换为SrAl2Si2O8相(Monoclinic,I2/c),晶胞参数a,b,c和晶胞体积都随Sr2+置换量呈线性增加,α,β和γ在置换量为0.1~0.7区间缓慢减小,超过0.7后呈线性急剧减小。位于250~410 nm区间的宽带激发光谱由4个激发峰构成,表观峰值位于356 nm。Eu2+占据两种格位形成两个发光中心,分别产生430和468 nm发射,宽带发射光谱位于390~550 nm区间,呈现近白色发光。控制Sr2+含量可使表观发射峰位置在408~434 nm之间移动,强度随Sr2+含量增加而增强。     

LaAlO3∶0.05Eu3+微晶的水热合成与表征

通过水热反应合成了六角形LaAlO3∶0.05Eu3+微晶样品,采用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、能量色散X射线(EDX)和荧光光谱(PL)对产物进行表征,讨论了反应温度和NaOH浓度对LaAlO3合成的影响.XRD分析表明,所合成的样品属三方晶系(空间群R3c),对LaAlO3∶0.05Eu3+样品的X射线粉末衍射数据进行Rietveld精修,最终R因子为Rp=6.79%,Rwp=8.96%;其晶胞参数为a=b=0.53636(2)nm,c=1.3101(1)nm.SEM分析表明,LaAlO3∶0.05Eu3+微晶具有六角形形貌,颗粒较均匀,平均尺寸约为4!m.PL分析表明,LaAlO3∶0.05Eu3+微晶的特征发射为Eu3+的5D0→7F1跃迁发射.     

(ZnBaLa)BO3∶Eu3+的合成与发光的研究

高温固相扩散法合成了发光材料Zn1．5xBa1．5yLa1-x-y-z)BO3∶Eu3+z(x+y+z＜0．4)．对样品进行了XRD和IR分析,结果表明：在空气中900 ℃条件下,合成了荧光体样品,LaBO3中La3+离子被部分Zn2+和Ba2+离子取代使晶系发生了变化,LaBO3属于正交晶系,而(Zn0．27Ba0．24La0．61)BO3∶Eu3+0．05经过XRD属于立方晶系,a=0.639 7,V=0.261 8 nm3．扫描电镜测其晶貌,平均粒度为22 μm左右．样品的激发光谱和发射光谱显示：在基质BO3结构中O2—Eu3+的CT带位于295 nm,Eu3+的强发射来自5D0→7F1和5D0→7F2跃迁,存在磁偶极和电偶极两种跃迁．     

CaLa4Si3O13:Eu3+红色荧光粉制备条件优化及助熔剂作用研究

采用高温固相法制备了CaLa4Si3O13:Eu3+红色荧光粉,研究了助熔剂总量、Li和B物质的量之比、烧成温度对发光性能的影响。以Eu3+的5 D0-7 F2发射强度为指标得出的最佳制备条件为:硼锂双助熔剂B和Li物质的量之比为1:1,总量为0.4 mol.mol-1,950℃预烧150 min,1150℃,240 min烧成。硼组分进入晶格置换硅,使晶胞参数a,c和晶胞体积V均逐渐减小,提高电/磁偶极跃迁强度比和总发光强度。助熔剂总量达到0.24 mol.mol-1后,进入基质的硼趋于饱和。硼组分起到助熔剂和基质组分置换双重作用。     

A new type of charge compensating mechanism in Ca5(PO4)3F:Eu phosphor

The X-ray powder diffraction, reflectance, photoluminescence, photoluminescence excitation and ESR spectra of Ca₅(PO₄)₃F:Eu³⁺ phosphor have been studied. Three distinct variants of calcium substitutional Eu³⁺-sites have been observed in this host and the charge compensating species related to each of these sites has been identified. It is noted that the host related trace impurities those have prospects of acting as charge compensator, and the reaction environment that exists during the preparation of the material, greatly influence the preferential substitution of different Ca²⁺-sites by the Eu³⁺ ions. It is also noted that the charge compensating species in a suitable case, takes part in the photophysical process of luminescence of the Eu³⁺.     

La7O6(BO3)(PO4)2:Eu3+/Tb3+荧光材料的制备及其光致发光性能

采用优化的高温固相方法制备了稀土离子Eu³⁺和Tb³⁺掺杂的La₇O₆（BO₃）（PO₄）₂系荧光材料,并对其物相行为、晶体结构、光致发光性能和热稳定性进行了详细研究。结果表明,La₇O₆（BO₃）（PO₄）₂：Eu³⁺材料在紫外光激发下能够发射出红光,发射光谱中最强发射峰位于616 nm处,为⁵D₀→⁷F₂特征能级跃迁,Eu³⁺的最优掺杂浓度为0.08,对应的CIE坐标为（0.610 2,0.382 3）;La₇O₆（BO₃）（PO₄）₂：Tb³⁺材料在紫外光激发下能够发射出绿光,发射光谱中最强发射峰位于544 nm处,对应Tb³⁺的⁵D₄→⁷F₅能级跃迁,Tb³⁺离子的最优掺杂浓度为0.15,对应的CIE坐标为（0.317 7,0.535 2）。此外,对2种材料的变温光谱分析发现Eu³⁺和Tb³⁺掺杂的La₇O₆（BO₃）（PO₄）₂荧光材料均具有良好的热稳定性。     

Synthesis,Persistent Luminescence,and Thermoluminescence Properties of Yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce,Nd, Dy,Ho, Er,Tm, Yb) and Orange‐Red Sr3−xBaxSiO5:Eu2+, Dy3+ Phosphor

Sunlight‐excitable orange or red persistent oxide phosphors with excellent performance are still in great need. Herein, an intense orange‐red Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ persistent luminescence phosphor was successfully developed by a two‐step design strategy. The XRD patterns, photoluminescence excitation and emission spectra, and the thermoluminescence spectra were investigated in detail. By adding non‐equivalent trivalent rare earth co‐dopants to introduce foreign trapping centers, the persistent luminescence performance of Eu²⁺ in Sr₃SiO₅ was significantly modified. The yellow persistent emission intensity of Eu²⁺ was greatly enhanced by a factor of 4.5 in Sr₃SiO₅:Eu²⁺,Nd³⁺ compared with the previously reported Sr₃SiO₅:Eu²⁺, Dy³⁺. Furthermore, Sr ions were replaced with equivalent Ba to give Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ phosphor, which shows yellow‐to‐orange‐red tunable persistent emissions from λ=570 to 591 nm as x is increased from 0 to 0.6. Additionally, the persistent emission intensity of Eu²⁺ is significantly improved by a factor of 2.7 in Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ (x=0.2) compared with Sr₃SiO₅:Eu²⁺,Dy³⁺. A possible mechanism for enhanced and tunable persistent luminescence behavior of Eu²⁺ in Sr_3?xBa_xSiO₅:Eu²⁺,RE³⁺ (RE=rare earth) is also proposed and discussed.     

Eu luminescence—a structural probe in BiCa4(PO4)3O, an apatite related phosphate

Eu³⁺ luminescence is studied in apatite-related phosphate BiCa₄(PO₄)₃O. Compositions of the formula Bi_1−xEu_xCa₄(PO₄)₃O [x=0.05, 0.1, 0.3, 0.5, 0.8 and 1.0] are synthesized and they are isostructural with parent BiCa₄(PO₄)₃O. Room temperature photoluminescence shows the various transitions ⁵D₀→⁷F_J(=0,1,2) of Eu³⁺. The emission results of compositions with different Eu³⁺ content show the difference in site occupancy of Eu³⁺ in Bi_1−xEu_xCa₄(PO₄)₃O. The intense ⁵D₀-⁷F₀ line at 574 nm for higher Eu³⁺ content is attributed to the presence of strongly covalent Eu-O bond that is possible by substituting Bi³⁺ in the Ca(2) site. This shows the preferential occupancy of Bi³⁺ in Ca(2) site and this has been attributed to the 6s² lone pair electrons of Bi³⁺. This is further confirmed by comparing the emission results with La_0.95Eu_0.05Ca₄(PO₄)₃O.     

Electrochemical behavior of single crystals of nonstoichiometric cerium(III) fluorides

The electrochemical properties of single crystals of cerium fluoride alloyed with bivalent cations Sr²⁺, Ca²⁺, Ba²⁺, Sr²⁺ + Ca²⁺, Sr²⁺ + Ba²⁺, Ba²⁺ + Ca²⁺ and also with La³⁺ and La³⁺ + Ba²⁺ cations are studied using the dynamic voltammetry and impedance spectroscopy. The conductivity of symmetrical cells with Ag electrodes is determined using the method of impedance spectroscopy in the frequency range from 450 to 5 kHz at the temperatures from 20 to 100°C: for CeF₃: Sr²⁺ (0.5 mol %) + Ba²⁺ (0.5 mol %), σ = σ₀ exp[(?0.284 ± 0.005/kT]; for CeF₃:Ca²⁺ (0.5 mol %) + Sr²⁺ (0.5 mol %), σ = σ₀ exp[(?0.292 ± 0.017/kT]. The steady-state and dynamic voltammogams of symmetrical electrochemical cells with nonpolarizable reference electrodes and CeF₃ single crystals alloyed with Sr²⁺, Ca²⁺, and Ba²⁺ bivalent cations exhibited ohmic polarization. For cells with CeF₃ containing La³⁺ as an admixture, a hysteresis was observed, which could not be eliminated by chemical and electrochemical treatment of crystals. In the dynamic voltammetric curves of asymmetric cells with nonpolarizable and silver electrode and CeF₃ crystals alloyed with Sr²⁺, Ca²⁺, and Ba²⁺, a range of ideal polarizability (from 0 to ～?2.7 V), and also cerium redox processes and silver fluorination-boundary regeneration were observed. In the dynamic voltammetric curves of asymmetric cells with CeF₃ containing La³⁺ admixture, no range of ideal polarizability was observed; however, the reactions of silver fluorination and reduction of solid-electrolyte cerium were well pronounced at the corresponding potentials.     

Crystal structure of Eu-doped M3MgSi2O8 (M: Ba, Sr, Ca) compounds and their emission properties

Emission properties of Eu²⁺-doped M₃MgSi₂O₈ (M: Ba, Sr, Ca) are discussed in terms of the crystal structure. When Ba²⁺ ions account for over one third of M²⁺ ions, M₃MgSi₂O₈ crystallizes in glaserite-type trigonal structure, while Ba-free compounds crystallize in merwinite-type monoclinic structure. Under UV excitation, the Eu²⁺-doped glaserite-type compounds exhibit an intense blue emission assigned to 5d-4f electron transition at about 435 nm, regardless of the molar ratio of Ba²⁺, Sr²⁺ and Ca²⁺ ions. By contrast, the Eu²⁺-doped merwinite-type compounds show an emission color sensitive to the ratio. A detailed analysis of the emission spectra reveals that the emission chromaticity for the Eu²⁺-doped M₃MgSi₂O₈ is composed of two emission peaks reflecting two different sites accommodating M²⁺ ion.     

Phase separation in the spin-state transition system of La1−xBaxCoO3

The magnetic and electric transport properties of La_1−xBa_xCoO₃ (0<x≤0.50) have been studied systematically. Two effects of substitution divalent ions on the spin-state transition of Co³⁺ have been differentiated for the substitution of Ba²⁺ for La³⁺ in La_1−xBa_xCoO₃. The first is the transition from low-spin state to high-spin state due to lattice expansion, and the second is the transition from low-spin state to intermediate-spin state caused by the strong hybridization between ligand (oxygen) 2p and Co 3d orbital with introduction of holes in the oxygen 2p orbital. Based on the two different spin-state transition mechanisms and experimental results, a phase separation model has been developed and a very detailed magnetic and electric phase diagram of La_1−xBa_xCoO₃ has been constructed.     

Synthesis and spectral characteristics of Sr2Y8(SiO4)6O2: Eu polycrystals

Spectral-luminescent characteristics of Sr₂Y₈(SiO₄)₆O₂: Eu powder crystal phosphor with the apatite structure and high-intensity luminescence of Eu³⁺ ions have been studied. The charge state of europium in the samples has been characterized by means of X-ray L₃-adsorption spectroscopy. It was established that Eu³⁺ forms two types of optical centers. Besides, luminescence of Eu²⁺ions was found. Reduction Eu³⁺→Eu²⁺ was considered, which may be due to vacancy formation in the 4f crystal lattice position and to negative charge transfer by this vacancy to two ions. Thus, in the silicate lattice there exist inhomogeneously distributed oxygen-deficient centers, which are responsible for nonradiative transfer of excitation energy to Eu³⁺ and Eu²⁺ ions. To study electron-vibrational interactions in the crystal phosphor samples, their IR and Raman spectra were examined. In the luminescence spectrum of Eu²⁺, a series of low-intensity bands caused by interaction of the 4f⁶5d state of Eu²⁺ with silicate lattice vibrations was observed.     

Cation and anion ordering in the layered oxyfluorides Sr3−xAxAlO4F (A=Ba, Ca)

The synthesis and structural characterization of mixed oxyfluorides of the type Sr_3−xA_xAlO₄F is reported, where A is either calcium or barium. In these compounds the fluoride and oxide ions are ordered onto two distinct crystallographic sites. There is also an ordering of the alkaline earth cations over two crystallographic sites upon substitution of Ba²⁺ or Ca²⁺ for Sr²⁺. The solid solubility limits extend to x∼1 for substitution of both barium and calcium, but the larger Ba²⁺ cations show a strong site preference for the ten-coordinate strontium sites, while the smaller Ca²⁺ cations prefer the eight-coordinate strontium sites.