Sr1-xZnxY2S4∶Er^3＋,Eu^2＋荧光粉的合成与发光特性的研究

采用碳酸盐前躯体高温分解法合成了Sr1-xZnxY2S4∶Er^3＋,Sr1-xZnxY2S4∶Eu^2＋和Sr1-xZnxY2S4∶Er^3＋,Eu^2＋红色荧光粉。XRD图谱表明,Zn^2＋掺杂量x〈0.2 mol时,粉末样品为CaFe2O4型正交晶体。Zn^2＋离子在Sr1-xZnxY2S4∶Er^3＋,Eu^2＋中的固溶量（xmol）对荧光粉的发射强度影响很大。随着Zn^2＋离子掺杂浓度的增加,Sr1-xZnxY2S4∶Er^3＋,Eu^2＋（SZYSEE）紫外区激发峰（200-413 nm）发生红移,并与可见光激发带（413-600 nm）形成一个连续的宽带谱,与紫外和GaN基LED芯片辐射都有良好的匹配性。当Zn^2＋掺杂量为0.1 mol时,SZYSEE的发光强度达到最大,其发光强度比未掺Zn2＋的增强10.7倍。Sr0.9Zn0.1Y1.76S4∶0.24Er^3＋,0.006Eu^2＋是一种潜在的白光LED用红色荧光粉。     

白光LED用红色荧光粉LixSr1-2xMoO4:Eux3+的制备及发光性质研究

采用高温固相法合成了白光LED用红色荧光材料LixSr1-2xMoO4:Eux3+,对样品分别进行了X射线衍射(XRD)分析、扫描电镜测试(SEM)和荧光光谱的测定.测试结果表明,LixSr1-2xMoO4:Eux3+荧光粉可以被近紫外光(uv)(394 nm)和蓝光(464 nm)有效地激发,且与没有掺杂Li+的荧光粉SrMoO4:Eu3+相比,发光强度得到了明显的增强.同时也讨论Li+和Eu3+的掺杂浓度对发光强度的影响.     

Sr2+含量对红色荧光粉Ca0.85-xSrxMoO4:Eu3+0.075,Li+0.075发光性能的影响

采用溶胶-凝胶法制备了Ca0.85-xSrxMoO4:Eu3+0.075,Li+0.075(x=0,0.05,0.1,0.15,0.2,0.3,0.4)系列红色荧光粉.对样品前驱体的热重分析表明:温度升高到540℃后样品质量基本上保持稳定,不再发生失重现象;此外,还对样品的结构和发光性能进行表征,实验结果表明:适量Sr2+取代部分的Ca2+不但没有改变Ca0.85MoO4:Eu3+,Li+的物相结构,而且明显提高了荧光粉Ca0.85MoO4:Eu3+,Li+的相对发光强度,其主要是由于加入少量的Sr2+使晶体发生了畸变,从而导致发光强度的增加.实验结果表明,Sr2+的最佳掺杂量为15%(原子分数).     

Li2Sr0.995-xSiO4:0.005Eu2+,xLa3+荧光粉的晶体结构与发光特性

采用高温固相反应法在还原气氛下制备了Li2Sr0.995-x SiO4:0.005Eu2+,xLa3+荧光粉。利用X射线衍射仪、荧光光谱仪和紫外可见分光光度计对样品的晶体结构、激发光谱、发射光谱与荧光衰减寿命以及漫反射光谱进行测试分析。实验结果表明:所制得的样品为单一相的Li2SrSiO4晶体结构化合物。Li2Sr0.995-x SiO4:0.005Eu2+,xLa3+荧光粉的激发光谱均呈现出宽激发带,其中最强的激发峰位于408 nm左右。在此波长激发下可得到峰值位于570 nm左右的宽波段单峰发射光谱,其对应于Eu2+离子4f65d1→4f7电子跃迁。La3+掺杂Li2SrSiO4:Eu2+荧光粉基质产生了晶格缺陷[2La·Sr·V″Sr],其可以吸收光能并将能量传递给发光中心离子Eu2+,进而增强Li2Sr0.995SiO4:0.005Eu2+荧光粉的发光强度。漫反射光谱和荧光衰减寿命测试结果也证实La3+掺杂能够增加Eu2+的激发态吸收能量,延长发光中心Eu2+离子荧光衰减寿命。     

镨和镱掺杂Ba2 SiO4:Eu2+荧光材料的合成与发光性能

采用高温固相反应法分别合成了变价稀土镨和镱离子掺杂的绿色荧光粉[Ba(2-n-1.5x)REx]SiO4:nEu2+ (n=0.03, RE=Pr, Yb;x=0, 0.02,0.05,0.10).结果表明: 所有合成荧光粉的激发峰均为250～400 nm的宽峰, 与近紫外LED的发射光波长相匹配.发射峰位于450～550 nm之间, 是Eu2+的5d-4f跃迁的典型发射.Pr3+和Yb3+的掺入并未改变Ba2SiO4:Eu2+的相组成, 但对荧光强度的影响大, 且与掺杂元素、掺杂量和煅烧温度相关.当掺杂Pr3+和Yb3+的量为x=0.02时, 经1150 ℃煅烧所得荧光粉的发光强度分别是未掺杂时的595%和168%.证明三价稀土离子掺杂可以导致基质中的电荷缺陷而敏化Eu2+离子的发光, 而变价稀土离子的掺杂可以大大提高电荷缺陷, 导致荧光强度的进一步提高.     

YVO_4:Eu~(3+),Al~(3+)荧光粉的制备及荧光性能研究

用高温固相法制备了Al3+掺杂的YVO4:Eu3+荧光粉。采用X射线粉末衍射(XRD)、环境扫描电镜(SEM)、荧光光谱(FL)等对样品进行了表征。分析了Al3+掺杂对YVO4:Eu样品晶体结构、晶胞参数和荧光性能的影响,并探讨了烧结温度对光谱性能的影响。研究结果表明:当Eu3+的浓度x(摩尔百分比)为4%,Al3+的浓度为1.5%时,在1100℃下烧结的样品其荧光性能最好,5D0→7F2处的发光强度约为未掺Al3+的2.5倍。由于Eu3+的7F2→5L6跃迁吸收,YVO4:Eu3+,Al3+荧光粉可在395 nm被有效激发。因此,YVO4:Eu3+,Al3+可以作为近紫外激发的白光LED红色荧光粉。     

Al18B4O33:Eu,Tb单基双掺杂荧光粉的制备及发光性能

以柠檬酸为络合剂,采用溶胶-凝胶法成功制备了Al18B4O33:Eu,Tb荧光粉.采用热分析仪、X射线衍射仪和扫描电镜分别对样品进行了热分析、结构和形貌分析,采用荧光光谱仪和亮度计测试样品的激发发射光谱和亮度.结果表明:前驱体先经700℃预烧,然后再于1100℃煅烧3h后,可获得粒度分布均匀、结晶性良好的Al18B4O33:Eu,Tb荧光粉;共掺杂Eu和Tb的Al18B4O33荧光粉可同时发出“三基色”所需要的特征发光;该荧光粉中同时存在Eu2+离子、Tb3+离子和Eu3+离子,在350～ 400 nm之间的紫外区域存在较强的激发峰,可被用于与紫外LED复合合成白光LED;通过研究Eu和Tb的掺杂量对荧光粉发光强度的影响发现,适量调节Eu和Tb的掺杂量可以改变Al18B4O33:Eu,Tb荧光粉的发光颜色和强度.     

近紫外LED用绿色荧光粉Ba0.11Sr2.89-2x-2yCexTbyNax+yAlO4F发光特性及Ce3+→Tb3+之间能量传递

高温固相法合成Ba0.11Sr2.89-2x-2yCexTbyNax+yAlO4F荧光粉,并用X射线衍射(XRD)、荧光光谱(PL)测定分析了其晶体结构及光谱性质。结果表明:当Tb3+掺杂量x=0.07时,发光强度最高,发射主峰位于545 nm,并进一步研究了Ce3+,Tb3+共掺的样品中Ce3+→Tb3+能量传递过程。其次,测试由近紫外LED(~380 nm)和三基色荧光粉(Ba0.11Sr2.89Ce0.01Tb0.07Na0.08AlO4F,BAM and Sr2Si5N8:Eu2+)封装的白光LED光电性能,其色品坐标(x=0.3223,y=0.3408),色温5500 K,显色指数为86.26。因此,Ba0.11Sr2.89-2x-2yCexTbyNax+yAlO4F可作为一种潜在的适用于近紫外LED激发的荧光材料。     

NaF助熔剂对Sr2MgSi2O7:Eu2+,Zr4+荧光粉结构及发光性能影响

在还原性气氛下采用高温固相法合成了适合近紫外(λex=375 nm)激发的光致发光蓝色荧光粉Sr2MgSi2O7:Eu2+,Zr4+,研究了NaF助熔剂对Sr2MgSi2O7:Eu2+,Zr4+荧光粉晶体结构、颗粒形貌及发光性能影响。结果表明:适量的NaF助熔剂有利于样品的晶化,所获得样品的颗粒形貌更加规整,能有效降低中间粒径(D50)并控制粒径分布;只含中间颗粒(D50)样品的发光强度高于含全颗粒样品的发光强度;NaF助熔剂最佳添加含量为6%(质量分数),可使样品的发光强度提高446%;掺杂适量的Zr4+有利于样品的发光强度的提高,最后探索NaF助熔剂及掺杂Zr4+离子提高发光性能的机制。     

Ca10(Si2O7)3Cl2:Eu2+Mn2+单-基质白光荧光粉的发光性质

用高温固相法合成了颜色可调的Ca10(Si2O7)3Cl2:Eu2+Mn2+荧光粉.研究了它的发光性质和Eu2+与Mn2+之间的能量传递.Eu2+离子在Ca10(Si2O7)3Cl2晶体中形成了峰值为426 nm和523 nm的5d→4f跃迁发光,Eu2+中心向Mn2+中心传递能量,敏化Mn2+离子4T1(4G)-6A1(6S)跃迁而产生585 nm的黄光发射.黄绿蓝3个发射带叠加在单一基质中实现了白光发射.3个发射带的激发谱范围位于250-480 nm处,Ca10(Si2O7)3Cl2:Eu2+Mn2+在紫外-近紫外波段(350～410 nm)范围内有很强的激发,是一种适合InGaN管芯激发的单一基质白光LED荧光粉.     

Sc2MgGa2 and Y2MgGa2

Scandium magnesium gallide, Sc₂MgGa₂, and yttrium magnesium gallide, Y₂MgGa₂, were synthesized from the corresponding elements by heating under an argon atmosphere in an induction furnace. These intermetallic compounds crystallize in the tetragonal Mo₂FeB₂‐type structure. All three crystallographically unique atoms occupy special positions and the site symmetries of (Sc/Y, Ga) and Mg are m2m and 4/m, respectively. The coordinations around Sc/Y, Mg and Ga are pentagonal (Sc/Y), tetragonal (Mg) and triangular (Ga) prisms, with four (Mg) or three (Ga) additional capping atoms leading to the coordination numbers [10], [8+4] and [6+3], respectively. The crystal structure of Sc₂MgGa₂ was determined from single‐crystal diffraction intensities and the isostructural Y₂MgGa₂ was identified from powder diffraction data.     

Electrochemical study of (NEt4)2Cl2FeS2MoS2 and (NEt4)2Cl2FeS2MoS2FeCl2

Summary The ability of [MoS₄]^2–, anions to be used as ligands for transition metal ions has been widely demonstrated, especially with Fe²⁺. The present study has been restricted to linear complexes such as (NEt₄)₂ [Cl₂FeS₂MoS₂] and (NEt₄)₂[Cl₂FeS₂MoS₂FeCl₂]. Their electrochemical properties are described: upon electrochemical reduction, these compounds yield MoS₂, as a black precipitate, and an iron complex in solution, assumed to be [SFeCl₂]^2–. The electrochemical reduction goes through two electron transfers, coupled with the breakdown of the molecular skeleton: a DISPl and an ECE mechanism. Depending on the solvent, the following equilibrium may be observed: [Cl₄Fe₂MoS₄]^2–[Cl₂FeMoS₄]^2–+FeCl₂. The equilibrium constant, K_D, was evaluated by differential pulse polarography. K_D is tightly related to the donor number of the solvent.     

Zur Kenntnis der Dialkalimetalldichalkogenide β-Na2S2, K2S2, α-Rb2S2, β-Rb2S2, K2Se2, Rb2Se2, α-K2Te2, β-K2Te2 und Rb2Te2

On Dialkali Metal Dichalcogenides β-Na₂S₂, K₂S₂, α-Rb₂S₂, β-Rb₂S₂, K₂Se₂, Rb₂Se₂, α-K₂Te₂, β-K₂Te₂ and Rb₂Te₂ The first presentation of pure samples of α- and β-Rb₂S₂, α- and β-K₂Te₂, and Rb₂Te₂ is described. Using single crystals of K₂S₂ and K₂Se₂, received by ammonothermal synthesis, the structure of the Na₂O₂ type and by using single crystals of β-Na₂S₂ and β-K₂Te₂ the Li₂O₂ type structure will be refined. By combined investigations with temperature-dependent Guinier-, neutron diffraction-, thermal analysis, and Raman-spectroscopy the nature of the monotropic phase transition from the Na₂O₂ type to the Li₂O₂ type will be explained by means of the examples α-/β-Na₂S₂ and α-/β-K₂Te₂. A further case of dimorphic condition as well as the monotropic phase transition of α- and β-Rb₂S₂ is presented. The existing areas of the structure fields of the dialkali metal dichalcogenides are limited by the model of the polar covalence.     

The alkali hypophosphites KH2PO2, RbH2PO2 and CsH2PO2

The structures of the hypophosphites KH₂PO₂ (potassium hypophosphite), RbH₂PO₂ (rubidium hypophosphite) and CsH₂PO₂ (caesium hypophosphite) have been determined by single‐crystal X‐ray diffraction. The structures consist of layers of alkali cations and hypophosphite anions, with the latter bridging four cations within the same layer. The Rb and Cs hypophosphites are isomorphous.     

Formal [(2+2)+2] and [(2+2)+(2+2)] nonconjugated dienediyne cascade cycloadditions

[reaction: see text] Fluoranthene 2 and heptacycle 3 are easily accessible from the reaction of diyne 1 and norbornadiene (NBD) in the presence of the rhodium catalyst. The unusual [(2+2)+(2+2)] adduct 3 was confirmed by the X-ray crystal structure analysis.     

Crystal Structures of [Bu2Sn(O2PPh2)2], [Ph2Sn(O2PPh2)2], and [PhClSn(O2PPh2)OMe]2. Raman Spectra of [Ph2Sn(O2PPh2)2] and [PhClSn(O2PPh2)OMe]2

[(n‐Bu)₂Sn(O₂PPh₂)₂] ( 1 ), and [Ph₂Sn(O₂PPh₂)₂] ( 2 ) have been synthesized by the reactions of R₂SnCl₂ (R=n‐Bu, Ph) with HO₂PPh₂ in Methanol. From the reaction of Ph₂SnCl₂ with diphenylphosphinic acid a third product [PhClSn(O₂PPh₂)OMe]₂ ( 3 ) could be isolated. X‐ray diffraction studies show 1 to crystallize in the monoclinic space group P2₁/c with a = 1303.7(1) pm, b = 2286.9(2) pm, c = 1063.1(1) pm, β = 94.383(6)°, and Z = 4. 2 crystallizes triclinic in the space group , the cell parameters being a = 1293.2(2) pm, b = 1478.5(4) pm, c = 1507.2(3) pm, α = 98.86(3)°, β = 109.63(2)°, γ = 114.88(2)°, and Z = 2. Both compounds form arrays of eight‐membered rings (SnOPO)₂ linked at the tin atoms to form chains of infinite length. The dimer 3 consists of a like ring, in which the tin atoms are bridged by methoxo groups. It crystallizes triclinic in space group with a = 946.4(1) pm, b = 963.7(1) pm, c = 1174.2(1) pm, α = 82.495(6)°, β = 66.451(6)°, γ = 74.922(6)°, and Z = 1 for the dimer. The Raman spectra of 2 and 3 are given and discussed.     

Die Photoionenspektren von SCl2, S2Cl2 und S2Br2

Photoionization Mass Spectra of SCl₂, S₂Cl₂, and S₂Br₂ Photoionization mass spectra of SCl₂, S₂Cl₂, and S₂Br₂ have been measured. Heats of formation, bond energies, and ionization potentials of fragments have been calculated from appearance potentials.