Ca8Mg（SiO4）4Cl2∶Eu2+,Ce3+,Mn2+绿色荧光粉发光性能及其应用研究

利用高温固相法,合成出Eu2+、Ce3+、Mn2+共掺的Ca8Mg(SiO4)4Cl2系列绿色荧光粉。通过XRD表征了这些荧光粉的结构,通过分子荧光光谱仪研究了它们的室温发光性能。首先调查了Eu2+掺杂的Ca8Mg(SiO4)4Cl2绿色荧光粉发光性能,随后引入Ce3+、Mn2+提高了Ca8Mg(SiO4)4Cl2∶Eu2+在紫外光区的吸收强度及绿光发射强度。最后将筛选出来的荧光粉与InGaN-LED芯片组装制作成单一绿光LED器件,利用Ca7.8215MgSi4O16Cl2∶0.0525Eu2+,0.056Ce3+,0.070Mn2+所制作成的绿光LED器件发光最强,在20mA电流激发下,此LED发很强的绿光,其电致发光光谱所对应的色坐标值为:x=0.26,y=0.55。     

微波辅助凝胶燃烧法合成红色荧光粉Ca2MgSi2O7:Eu3+及性质研究

采用微波辅助凝胶燃烧法制备了Ca2MgSi2O7∶Eu3+红色荧光粉,运用XRD、荧光分光光度计等对合成样品进行分析表征,并探讨了焙烧温度、助熔剂用量、Eu3+浓度等对样品发光性能的影响。结果表明:所得样品为四方晶系的Ca2MgSi2O7晶体结构。Ca2MgSi2O7∶Eu3+的激发光谱由一宽带和一组锐线峰组成,分别归属于Eu3+-O2-之间的电荷迁移态和Eu3+的f→f跃迁。样品的发射光谱主要由两个强发射峰组成,分别位于591 nm和619 nm处,属于Eu3+的5D0→7F1磁偶极跃迁和5D0→7F2的电偶极跃迁。研究发现:当焙烧温度为1000℃、助熔剂H3BO3用量为15%时,样品发光性能较好;Eu3+浓度(x)对样品Ca2-xMgSi2O7∶Eu3x+的发光强度影响较大,当Eu3+浓度x在0.02～0.16范围内变化时,随着Eu3+浓度的增加,样品的发光强度不断增加,未出现明显的浓度猝灭现象。     

LaNbO4∶Dy3+,Ca2+荧光粉的制备及发光性能研究

为提高蓝绿色荧光粉的发光性能，本文采用传统的高温固相法合成LaNbO₄∶Dy³⁺及LaNbO₄∶Dy³⁺,Ca²⁺荧光粉样品。通过测试样品的XRD、荧光光谱和CIE色度坐标，研究Dy³⁺单掺，Dy³⁺、Ca²⁺共掺对LaNbO₄荧光粉性能的影响。结果表明：LaNbO₄∶Dy³⁺及LaNbO₄∶Dy³⁺,Ca²⁺荧光粉的衍射峰都与标准卡衍射峰的位置相匹配。样品的激发光谱均由两个宽带激发峰和一系列尖锐激发峰组成，LaNbO₄∶Dy³⁺和LaNbO₄∶Dy³⁺,Ca²⁺样品的最强激发峰位分别是387和472 nm。在波长为387 nm激发下，样品的最强发射峰值分别是575和477 ...     

Eu2+掺杂的Sr10P6O24C12荧光粉的制备及性能

采用固相法制备了Sr10P6O24Cl2∶Eu2+荧光粉,确定了适用于Sr10P6O24Cl2∶Eu2+荧光粉制备的方法及工艺条件,并利用XRD、激发光谱和发射光谱等方法分析表征样品的结构和光学性能.研究了Eu2在基质中所占的格位以及Eu2+浓度对样品发光强度的影响.实验结果表明,原料在900～1100℃下烧结4h,制得了能够发射较好蓝光的Sr10P6O24Cl2∶Eu2+荧光粉.     

Ce3+在Ba2ZnB2O6中的晶体学格位及其发光性能研究

通过高温固相法合成了Ba2ZnB2O6∶Ce3+蓝色荧光粉.通过XRD、Rietveld结构精修、激发和发射光谱、荧光衰减曲线以及变温荧光光谱等,对荧光粉的晶体结构和发光性能进行了研究.结果表明:Ce3+的掺入并未对基质的晶格结构产生影响,在350 nm近紫外光激发下,Ba2ZnB2O6∶xCe3+的发射峰为位于430 nm的不对称的宽谱,最佳掺杂浓度为x=0.01,Ce3+在Ba2ZnB2O6晶格中占据Bal和Ba3两种格位,随掺杂浓度升高更倾向于占据Ba3位.Ce3+的择优占位使荧光粉的发光由蓝光向蓝绿色区域发生了明显的漂移.     

宽带发射Ca2KMg2V3O12:Eu3+荧光粉的制备及其发光性能研究

本文通过高温固相法合成了新型的宽带发射Ca2KMg2V3O12:Eu3+荧光粉,并利用X射线粉末衍射仪,荧光光谱仪等表征手段对荧光粉的晶体结构及其发光性能进行了分析;探讨了Ca2KMg2V3O12荧光粉的自激活发光机理和Eu3+掺杂浓度对发光性能的影响.结果表明:所制备的样品为立方晶系Ca2KMg2V3O12晶体.在紫外光的激发下,Ca2KMg2V3O12:Eu3+既表现出[VO4]基团的宽带发射,又表现出Eu3+的特征发射,同时两者之间存在能量传递.Ca2KMg2V3O12:Eu3+荧光粉是一种良好的自激活发光材料,在紫外光激发的白光LED上具有潜在的应用前景.     

白光LED用Ca0.5-xWO4∶Eu0.253+Li0.25+Srx2+红色荧光粉的合成及发光性能研究

采用溶胶-凝胶燃烧法合成了不同Sr2+掺杂浓度的Ca0.5-xWO4∶Eu0.253+Li0.25+Srx2+(x=0,0.05,0.10,0.15,0.20,0.25)红色荧光粉,分别采用X射线衍射(XRD)、扫描电镜(SEM)和荧光分光光度计对荧光粉的结构、微观形貌和发光特性进行表征.结果表明,在500℃低温下煅烧4h可得到纯白钨矿结构的Ca05WO4∶Eu0.253+Li0.25+荧光粉,且荧光粉的颗粒随着煅烧温度的升高而增大,800℃合成的晶粒尺寸比较均匀,平均粒径在1～2 μm左右.Ca0.5-xWO4∶Eu0.253+Li0.25+Srx2+系列荧光粉均可以被393 nm和464 nm有效激发,其发射主峰值位于615 nm,属于Eu3的5D0→7F2跃迁.同时还系统研究了Sr2+的不同掺杂浓度对荧光粉发光性能的影响.Ca05-xWO4∶Eu0.253+Li0.25+Srx2+荧光粉中Sr2+的最佳掺杂浓度为x取0.15.     

LaP3O9∶Eu3+荧光粉的制备及发光性能研究

以La2O3、Eu2O3和(NaPO3)6为原料,采用共沉淀法制备了LaP3O9∶Eu3+荧光粉,并对其发光性能进行了分析。结果表明:该荧光粉的最强吸收峰位于391 nm处;两个发射峰分别位于587 nm和616 nm处,且两峰发光强度相近,说明Eu3+在LaP3O9∶Eu3+晶体场中处于具有非反演中心对称的格位;与LaPO4∶Eu3+荧光粉相比LaP3O9∶Eu3+发出的红光色饱和度更高;Eu3+在LaP3O9∶Eu3+晶体荧光粉中的掺杂浓度为8at%时,发光强度最大。     

水热法制备Y2O2S∶Dy3+,Mg2+,Ti4+白色长余辉微纳米材料及发光性能

采用水热法制备了白色长余辉微纳米发光材料Y2O2S∶x Dy3+,Mg2+,Ti4+(x=0.5%,1.0%,1.5%,2.0%,2.5%),利用X射线粉末衍射(XRD)、扫描电镜(SEM)、激发和发射光谱、色度坐标、余辉曲线和热释光谱对样品进行表征。结果表明:煅烧后,样品的形貌为颗粒状,其粒径在150~250 nm之间;在359 nm的紫外光激发下,样品在488 nm和579 nm处有两个很强的发射峰,它们分别对应于Dy3+的蓝色跃迁(4F9/2→6H15/2)和黄色跃迁(4F9/2→6H13/2),适当比例的黄光和蓝光混合可以产生白光;当Dy3+浓度为2.0%(摩尔分数)时,样品的余辉性能最佳,用254 nm的低压汞灯照射10 min后,余辉时间可达到3600 s(≥1 mcd/m2)以上,与同样温度下高温固相法或溶胶凝胶法所制备样品的相比,其余辉性能得到了很大改善。     

通过SiO2涂层改善BaSi2O2N2∶Eu2荧光粉的热性能

本文研究了SiO2涂层对BaSi2O2N2∶ Eu2蓝绿色荧光粉发光性能和热性能的影响.采用溶胶-凝胶法制备了SiO2包覆的BaSi2O2N2∶Eu2+蓝绿色荧光粉.实验结果表明,最佳镀膜量为6wt;,当镀膜量大于此值时,荧光粉亮度迅速降低.涂覆SiO2后,在150℃下BaSi2O2 N2∶Eu2荧光粉的热猝灭性能提高了2.4;,在500℃热降解后荧光粉的发光性能提高了15;.SiO2涂层显著提高了BaSi2O2N2∶Eu2+荧光粉的热稳定性.SiO2涂层的作用机理是在荧光粉表面和氧化气氛之间形成阻挡层,保护Eu2的发光中心在热加热过程中不被氧化.     

表面活性剂辅助合成Y2O2S:Eu3+,Mg2+,Ti4+红色长余辉材料

以表面活性剂十二烷基硫酸钠为均匀分散剂,通过液相与固相相结合的方法制备了Y2O2S∶Eu3+,Mg2,Ti4+红色长余辉材料.采用X射线衍射(XRD)、扫描电镜(SEM)、激发与发射光谱、热释光谱等手段对材料进行了表征.研究结果表明,与高温固相法相比,样品的最低合成温度与最佳合成温度均降低了200～300℃,其发光特性没有改变,表面活性剂的添加影响了样品的形貌.同时,对表面活性剂引入后,Y2O2S∶Eu3+,Mg2+,Ti4+的生长机制和发光机理进行了讨论.     

Energy transfer in Eu3+-Yb3+ and Tb3+-Yb3+ system in glasses

The behavior of the phonon-assisted energy transfer between trivalent rare-earth ions in glasses was investigated. The ions Eu³⁺ and Tb³⁺ as energy donors and Yb³⁺ as acceptor were selected. The energy gap between the levels of the donor and acceptor was estimated on the basis of the energy diagram of each ion determined from absorption and emission spectra. The probability for the transfers of (Eu, ⁵D₀-⁷F₆): (Yb, ${}^2\text{F}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{-}{}^2\text{F}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$) and (Tb, ⁵D₄-⁷F₀): (Yb, ${}^2\text{F}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{-}{}^2\text{F}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$) in silicate, borosilicate, phosphate and germanate glasses was measured in the temperature range of liquid-nitrogen temperature - 650K. The probability of transfer was the smallest in phosphate glass and B₂O₃ had the effect of increasing it. In germanate glass the dependence of the probability of the energy gap was relatively weak. These results were correlated to the difference in the phonon energy and the strength of the electron-lattice coupling in each glass.     

Solarization mechanism of glass containing Ce3+ and As5+

The solarization mechanism in a glass containing both Ce³⁺ and As⁵⁺, 16Na₂O·11CaO·73SiO₂:0.15AsO_x·0.015CeO_x (in mol.%), is newly proposed by elucidating the valence and coordination structure of arsenic after the photochemical reaction, the mechanism being traditionally expressed as

$\text{2}\text{Ce}{}^{\mathrm{3+}}\text{+}\text{As}{}^{\mathrm{5+}}\text{→}\text{hv}\text{2}\text{Ce}{}^{\mathrm{4+}}\text{+}\text{As}{}^{\mathrm{3+}}$

ESR hyperfine quartets due to an As⁴⁺ ranging from 0.1 to 0.5 T built up on UV-irradiation and their line shape varied with the duration of the irradiation. The line shape analysis of the ESR spectra employing a computer simulation technique has led to the following conclusions; (1) As⁵⁺ is reduced to As⁴⁺ in the solarization process. (2) The geometry around the As⁴⁺ in the solarized glass is tetrahedral during the early stage and trigonal-pyramidal during the latter stage of the reaction.     

State of Fe3+ ion and Fe3+ −F− interaction in calcium fluorosilicate glasses

The state of Fe³⁺ ions and Fe³⁺ ?F^? interaction in calcium fluorosilicate glasses xCaF₂·(1- x)CaO·SiO₂) (0 ≤ x ≤ 0.3) containing a small amount of iron were investigated by ESR spectroscopy. Two resonances observed near g = 2.0 and g = 4.3 were assigned to dipole-dipole interacted Fe³⁺ ions and Fe³⁺ ions in a rhombic crystal field, respectively. The fraction of Fe³⁺ ions in a rhombic crystal field decreased and that of dipole-dipole interacted Fe³⁺ ions increased with increasing Fe₂O₃ content. It was found that the quantity of dipole-dipole interacted Fe³⁺ ions depends on the negative partial charge of fluorine ions and shows a maximum at 10 mol% CaF₂ (x = 0.2). The maximum is attributed to the largest difference between absolute values of the ionic potentials of ferric and fluorine ions which is caused by the smallest negative partial charge of flourine at 10 mol% CaF₂.     

Crystal structure of R[UO2(CH3COO)3] (R = NH 4+ , K+, or Cs+)

The single crystal structure of NH₄[UO₂(CH₃COO)₃] (I), K[UO₂(CH₃COO)₃] (II), and Cs[UO₂(CH₃COO)₃] (III) is studied by X-ray diffraction. I and II crystallize in the tetragonal crystal system. The crystal data are as follows: a = 13.6985(3) and c = 27.5678(14) ?, V = 5173.1(3) ?³, space group I4₁/a, Z = 16, and R = 0.023 for I; a = 13.8890(5) and c = 26.0839(18) ?, V = 5031.7(4) ?³, space group I4₁/a, Z = 16, and R = 0.037 for II. Crystals III are orthorhombic, a = 18.176(2), b = 13.119(2), and c = 22.088(4) ?, V = 5267(1)?³, space group Pbca, Z = 16, and R = 0.0424. In structures I–III, the uranium-containing structural units are represented by discrete mononuclear [UO₂(CH₃COO)₃]⁻ groups, which belong to the AB ₃⁰¹ (A = UO₂²⁺, B ⁰¹=CH₃COO⁻) crystal chemical group of uranyl complexes.     

The investigation of the magnetic interaction between Cu2+ and V4+ ions in x(CuO·2V2O5)(1 − x)[2B2O3·K2O] glasses

EPR and magnetic susceptibility measurements have been performed on (CuO·2V₂O₅)(1?x)[2B₂O₃·K_2O] glasses with 0 ? x ? 40 mol. %.For x < 10 mol.%, both Cu²⁺ and V⁴⁺ ions are present mostly as the isolated species. The values of MO coefficients indicate a high covalent degree of the transition metal (TM)-oxygen bonds. Also, the EPR parameters suggest the presence of strong (TM)-oxygen bonds along the 0_z axis, which lead to an octahedral (Oh) symmetry component at TM ions sites.In the case of 10 ? x ? 40 mol.%, the dipole-dipole and superexchange interactions occur between transition metal ions, which determine a broad resonance line at $\text{g ? 2}$. The strong interactions between Cu²⁺ and V⁴⁺ ions give rise to the exchange coupled Cu²⁺ V⁴⁺ pairs in the studied glasses with x > 10 mol.% (y > 3.9 mol.%).     

Effect of quenching rate and annealing on ESR of Cu2+ and γ-induced Cd+ in low alkali borate glasses

A new ESR hyperfine structure (hfs) of Cu²⁺ was detected in moderately (cooling rate ≈ 3 K/s) and rapidly (10³–10⁵K/s) quenched borate glasses with Na₂O content smaller than 5 mol% in addition to the already reported three patterns, spectra I, II and III, for the moderately quenched borate glasses with 5 ? [Na₂O]?13, 20 ? [Na₂O] ?37 and 55 ? [Na₂O] ? 75, respectively. The ESR parameters of this spectrum were much the same as those of II, but a significant difference was observed between thermal stabilities of these spectra. The newly observed spectrum was named spectrum II′. A superposition of spectra II′ and I was seen in low alkali borate glasses ([Na₂O] ? 5 mol%). The relative intensity of II′ to I increased remarkably with increasing quenching rate of the melts and with decreasing alkali content under the same quenching condition. In addition, spectrum II′ was found to relax into I upon thermal annealing of the glasses. Similar changes were observed also in ESR of the γ-induced Cd⁺ with 5s¹ electronic configuration. A tentative model to account for the spectral changes was proposed on the basis of the characteristics of B—O bonding.     

Crystal structure and hydrogen bonding of propargylammonium hexafluorosilicate, 2(C3H6N)+ (SiF6)2?

The X-ray crystal structure of propargylammonium hexafluorosilicate, 2(C₃H₆N)⁺ (SiF₆)²⁻, is determined. The SiF₆ anion is involved in N−H...F and C−H...F interactions with eight surrounding cations. This involves two-three-and four-center N−H...F hydrogen bonds, and additional C−H...F interactions with C...F distances down to 2.963(6) ?. The alkynyl C−H donors form only C−H...F interactions of unfavorable geometries.     

白光LED用红色荧光粉SrMoO4: Eu3+,Gd3+的制备与表征

采用共沉淀法合成了红色荧光粉Sr1-x-yMoO4∶ Eu3+x,Gd3+y,分别对样品进行了X射线衍射(XRD)分析、扫面电镜(SEM)和荧光光谱(PL)的测定.结果表明:所合成的样品均为单一纯相四方晶系结构,添加Gd3+(为0.35mol时)使主衍射峰的位置右移了0.35°;SEM照片显示:SrMoO4∶ Eu3+和SrMoO4∶Eu3+,Gd3+颗粒尺寸分布相对均匀,为类方块状,颗粒大小约为1～3μm;Gd3+和Eu3+的共掺得到的SrMoO4∶ Eu3+,Gd3+在616 nm处主发射峰的发光强度约是SrMoO4∶Eu3+的2.09倍;当掺杂x=0.25 mol和y=0.35 mol时,在近紫外光(395 nm)激发下,SrMoO4Eu3+,Gd3+得到616 nm处红光发射极峰.     

Single crystals of the fluorite nonstoichiometric phase Eu 0.9162+ Eu 0.0843+ F2.084 (conductivity, transmission, and hardness)

The nonstoichiometric phase EuF_2+x has been obtained via the partial reduction of EuF₃ by elementary Si at 900–1100°C. Eu_0.916²⁺Eu_0.084³⁺F_2.084 (EuF_2.084) single crystals have been grown from melt by the Bridgman method in a fluorinating atmosphere. These crystals belong to the CaF₂ structure type (sp. gr. Fm $ \bar 3 $ \bar 3 m) with the cubic lattice parameter a = 5.8287(2) ?, are transparent in the spectral range of 0.5–11.3 μm, and have microhardness H _μ = 3.12 ± 0.13 GPa and ionic conductivity σ = 1.4 × 10⁻⁵ S/cm at 400°C with the ion transport activation energy E _a = 1.10 ± 0.05 eV. The physicochemical characteristics of the fluorite phases in the EuF₂ − EuF₃ systems are similar to those of the phases in the SrF₂ − EuF₃ and SrF₂ − GdF₃ systems due to the similar lattice parameters of the EuF₂ and SrF₂ components. Europium difluoride supplements the list of fluorite components MF₂ (M = Ca, Sr, Ba, Cd, Pb), which are crystal matrices for nonstoichiometric (nanostructured) fluoride materials M _{1 − x} R _x F_{2 + x} (R are rare earth elements).