共查询到20条相似文献,搜索用时 31 毫秒
1.
R. A. Stukan T. V. Dudareva Yu. N. Kil’yanov A. V. Polyakova 《Russian Journal of Inorganic Chemistry》2006,51(1):1-4
A tetragonal 123 phase with the composition close to CeLa2 { Cu
2
2+
} [Mg2+]O8 (the braces indicate the Cu(2) positions; the brackets indicate the Cu(1) positions) with the parameters a = b = 0.3909(3) nm, c = 1.6591(8) nm was prepared at 860°C under an oxygen atmosphere with an elevated oxygen pressure. When the lanthanum-for-barium
substitution was incomplete, the resulting 123 phase had the composition close to CeLa1.7Ba0.3{ Cu
1.7
2+
} [Mg]O8 with the unit cell parameters a = b = 0.3868(3) nm, c = 1.6578(8) nm that contains Cu3+ in the Cu(2) positions. The partial substitution of barium for lanthanum (the melting point of barium oxide is almost 500°C
lower that of the lanthanum oxide) appreciably facilitated the synthesis: the 123 phase in this sample was more than 90%.
The existence of Cu3+ in the Cu(2) positions enhanced the electrical conductivity of the sample. 相似文献
2.
Compounds Ce2TiO5, Ce2Ti2O7, and Ce4Ti9O24 were prepared by heating appropriate mixtures of solids containing Ce4+ and Ti3+ or Ti which were placed in a platinum-silica-ampoule combination at T = 1250°C (3d) under vacuum. The new compounds were characterized by powder patterns. We obtained Ce2TiO5 which is isotypic to La2TiO5 and crystallizes in the Y2TiO5-type (space group Pnma) with a = 10.877(6) Å, b = 3.893(1) Å, c = 11.389(8) Å, Z = 4. Ce2Ti2O7 is isotypic to La2Ti2O7 and crystallizes in the monoclinic Ca2Nb2O7 type (space group P 21) with a = 7.776(6) Å, b = 5.515(4) Å, c = 12.999(6) Å, β = 98.36(5), Z = 4. The compound Ce4Ti9O24 crystallizes orthorhombic with a = 14.082(4) Å, b = 35.419(8) Å, c = 14.516(4) Å, Z = 16. The new cerium titanate Ce4Ti9O24 is isotypic to Nd4Ti9O24 (space group Fddd (No. 70)) which represents a novel type of structure. 相似文献
3.
采用高温固相法在空气中合成了Ba1.97-yZn1-xMgxSi2O7:0.03Eu,yCe3+系列荧光粉。分别采用X-射线衍射和荧光光谱对所合成荧光粉的物相和发光性质进行了表征。在紫外光330~360 nm激发下,固溶体荧光粉Ba1.97-yZn1-xMgxSi2O7:0.03Eu的发射光谱在350~725 nm范围内呈现多谱峰发射,360和500 nm处有强的宽带发射属于Eu2+离子的4f65d1-4f7跃迁,590~725 nm红光区窄带谱源于Eu3+的5D0-7FJ (J=1,2,3,4)跃迁,这表明,在空气气氛中,部分Eu3+在Ba1.97-yZn1-xMgxSi2O7基质中被还原成了Eu2+;当x=0.1时,荧光粉Ba1.97Zn0.9Mg0.1Si2O7:0.03Eu的绿色发光最强,表明Eu3+被还原成Eu2+离子的程度最大。当共掺入Ce3+离子后,形成Ba1.97-yZn0.9Mg0.1Si2O7:0.03Eu,yCe3+荧光粉体系,其发光随着Ce3+离子浓度的增大由蓝绿区经白光区到达橙红区;发现名义组成为Ba1.96Zn0.9Mg0.1Si2O7:0.01Ce3+,0.03Eu的荧光粉的色坐标为(0.323,0.311),接近理想白光,是一种有潜在应用价值的白光荧光粉。讨论了稀土离子在Ba2Zn0.9Mg0.1Si2O7基质中的能量传递与发光机理。 相似文献
4.
The nitridosilicate chloride Ba1.63La7.39Si11N23Cl0.42:Ce3+ was synthesized by metathesis reaction starting from LaCl3, BaH2, CeF3 and the product of the ammonolysis of Si2Cl6. The title compound is stable towards air and moisture. Diffraction data of a microcrystal were recorded using microfocused synchrotron radiation. X‐ray spectroscopy confirms the chemical composition of the crystal. IR spectra corroborate absence of N–H bonds. The compound is homeotypic to Ba2Nd7Si11N23 and crystallizes in space group Cmmm with a = 11.009(3), b = 23.243(8), c = 9.706(4) Å and Z = 4, R1(all) = 0.0174. According to bond valence sum calculations, some crystallographic positions show complete occupancy by Ba or La whereas others contain significant amounts of both elements. In contrast to the structure prototype Ba2Nd7Si11N23, Ba1.63La7.39Si11N23Cl0.42:Ce3+ contains chloride ions in channels of the SiN4 tetrahedra network, hinting at various substitution possibilities of the complex zeolite‐like structure. 相似文献
5.
The phase of the composition CaBaLaCu2FeO7.5 is synthesized from the previously obtained CaCuO2, La2Cu2O5, and BaFeO2 double oxides enriched up to 14.7% in 57Fe. The phase has the orthorhombic crystal system with the unit cell parameters as follows: a = 0.3882(3) nm, b = 0.3911(3) nm, c = 1.1823(8) nm. Based on the M?sbauer spectra analysis, the conclusion is drawn that iron atoms occupy only Cu(1) sites in
the lattice, while more than 90% of them are in the Fe4+ valence state (80% of these atoms have the tetragonal pyramidal coordination). 相似文献
6.
R. A. Stukan V. G. Bekeshev Yu. D. Strel’tsova 《Russian Journal of Inorganic Chemistry》2013,58(2):117-119
Tetragonal (123) phases of compositions Ca0.7Na0.3Ba2Cu2WO8, CaBa1.7Na0.3Cu2WO8, and CaBa1.7K0.3Cu2WO8, where tungsten occurs in Cu(1) positions and Cu3+ is in Cu(2) positions, were prepared from CaWO4, BaCuO2, and sodium and potassium nitrates at 1073 K in an oxygen flow. These phases constitute at least 90% of the samples; their unit call parameters are as follows: a = b = 0.4177(3) nm, c = 1.2561(8) nm; a = b = 0.4182(3) nm, c = 1.2564(8) nm; and a = b = 0.4194(3) nm, c = 1.2603(8) nm, respectively. Their X-ray diffraction patterns feature peaks that indicate a superstructure with all three unit cell parameters being doubled. The samples have weak conductive properties (room-temperature electrical conductivity ranges between 10?6 and 10?7 Ohm?1 cm?1). Conductivity versus temperature curves are indicative of the semiconductor character of the samples. Superconducting transitions do not occur up to 65 K. 相似文献
7.
利用溶胶-凝胶方法在800 ℃焙烧10 h后, 合成了固溶体Ce1-xNdxO2-δ (x=0.05~0.55), X射线衍射(XRD)测试表明固溶体已经形成立方萤石结构; 电子顺磁共振谱(EPR)研究表明在固溶体Ce1-xNdxO2-δ中随着掺杂量x的增大, Ce3+离子含量减少, 说明掺杂Nd3+离子可以抑制Ce4+的还原; 交流阻抗谱的测量表明固溶体Ce0.9Nd0.1O2-d 具有离子导电特性, 600和700 ℃时的电导率分别为4.25×10-3和1.12×10-2 S•cm-1, 活化能为0.68 eV. 相似文献
8.
Qinxing Xie Christof Kubata Michael Wörle Reinhard Nesper Prof. Dr. 《无机化学与普通化学杂志》2008,634(14):2469-2476
The isostructural compounds Yb2MgSi2, La2.05Mg0.95Si2, and Ce2.05Mg0.95Si2, as well as Yb2Li0.5Ge2 and Yb1.75Mg0.75Si2, respectively, were synthesized from stoichiometric mixtures of the corresponding elements in sealed Nb‐ ampoules under argon atmosphere. The structures were determined by single crystal X‐ray diffraction: Yb2MgSi2 (P4/mbm (No. 127), a = 7.056(1), c = 4.130(1) Å3, Z = 2), La2.05Mg0.95Si2 (P4/mbm, a = 7.544(1), c = 4.464(1) Å3, Z = 2), and Ce2.05Mg0.95Si2 (P4/mbm, a = 7.425(1), c = 4.370(1) Å3, Z = 2), Yb2Li0.5Ge2 (Pnma (No. 62), a = 7.0601(6), b = 14.628(1), c = 7.6160(7) Å, V = 786.5Å3, Z = 4), Yb1.75Mg0.75Si2 (Pnma, a = 6.9796(1), b = 14.4009(1), c = 7.5357(1) Å, V = 757.43(2) Å3, Z = 4). All compounds contain exclusively Tt‐Tt dumb‐bells (Tt = Si, Ge). The Si‐Si Zintl anions exhibit only very small variations of bond lengths which seem to be more due to cation matrix effects than to effective bond orders. 相似文献
9.
Stefan Linsinger Selcan Tuncel Wilfried Hermes Matthias Eul Bernard Chevalier Rainer Pöttgen Prof. Dr. 《无机化学与普通化学杂志》2009,635(2):282-286
The rare earth‐rich compounds RE23Rh7Mg4 (RE = La, Ce, Pr, Nd, Sm, Gd) were prepared by induction‐melting the elements in sealed tantalum tubes. The new compounds were characterized by X‐ray powder diffraction. They crystallize with the hexagonal Pr23Ir7Mg4 type structure, space group P63mc. The structures of La23Rh7Mg4 (a = 1019.1(1), c = 2303.7(4) pm, wR2 = 0.0827, 1979 F2 values, 69 variables), Nd23Rh7Mg4 (a = 995.4(2), c = 2242.3(5) pm, wR2 = 0.0592, 2555 F2 values, 74 variables) and Gd23Rh6.86(5)Mg4 (a = 980.5(2), c = 2205.9(5) pm, wR2 = 0.0390, 2083 F2 values, 71 variables) were refined from single crystal X‐ray diffractometer data. The three crystallographically different rhodium atoms have trigonal prismatic rare earth coordination with short RE–Rh distances (283–300 pm in Nd23Rh7Mg4). The prisms are condensed via common edges, leading to a rigid three‐dimensional network in which isolated Mg4 tetrahedra (312–317 pm Mg–Mg in Nd23Rh7Mg4) are embedded. Temperature dependent magnetic susceptibility data of Ce23Rh7Mg4 indicate Curie‐Weiss behavior with an experimental magnetic moment of 2.52(1) μB/Ce atom, indicative for stable trivalent cerium. Antiferromagnetic ordering is evident at 2.9 K. 相似文献
10.
11.
A. Oká und M. Vrchlabský 《Fresenius' Journal of Analytical Chemistry》1963,195(5):338-342
Zusammenfassung Bei der photometrischen Untersuchung der Reaktion von Sc3+ mit Glyoxal-bis(2-hydroxyanil) (GBHA) wurden die Bedingungen für die Bildung von Komplexen festgelegt und eine empfindliche Methode der photometrischen Sc-Bestimmung ausgearbeitet. Diese ist in Anwesenheit von Nd3+, Y3+, La3+ und Al3+ anwendbar, wird aber von UO2
2+, Cu2+, Ce3+, Ti4+, Ce4++ und Tl3+ gestört. 相似文献
12.
Summary The chelation behaviour of the complexes of La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Y3+, Tb3+, Dy3+, Ho3+ with biologically active 2-Hydroxy-1-naphthaldehyde semicarbazone (HNAS) has been studied potentiometrically in 75% (v/v) dioxane-water medium at various ionic strengths. The method of Bjerrum and Calvin, as modified by Irving and Rossotti has been used to find out the values of n andpL. The formation constants of metal chelates and the values ofS
min have been calculated. The order of formation constants of chelates was found to be: La3+3+3+3+3+3+3+3+3+3+3+.
Physikochemische Untersuchungen zur Komplexierung von biologisch aktivem 2-Hydroxy-1-naphthaldehyd-Semicarbazon (HNAS) mit Lanthanoiden
Zusammenfassung Das Chelierungsverhalten von La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Y3+, Tb3+, Dy3+ und Ho3+ mit 2-Hydroxy-1-naphthaldehydsemicarbazon (HNAS) wurde potentiometrisch in 75% (v/v) Dioxan-Wasser bei verschiedenen Ionenstärken untersucht. Die Werte für n undpL wurden nach der Methode von Bjerrum und Calvin in der Modifikation von Irving und Rossotti bestimmt. Die Komplexbildungskonstanten der Metallchelate und die WerteS min wurden ermittelt. Die Reihung der Komplexbildungskonstanten war La3+相似文献3+ 3+ 3+ 3+ 3+ 3+ 3+ 3+ 3 3+.
13.
采用高温固相法在空气中合成了Ba1.97-yZn1-xMgxSi2O7∶0.03Eu,y Ce3+系列荧光粉。分别采用X-射线衍射和荧光光谱对所合成荧光粉的物相和发光性质进行了表征。在紫外光330~360 nm激发下,固溶体荧光粉Ba1.97-yZn1-xMgxSi2O7∶0.03Eu的发射光谱在350~725 nm范围内呈现多谱峰发射,360和500 nm处有强的宽带发射属于Eu2+离子的4f 65d1-4f 7跃迁,590~725 nm红光区窄带谱源于Eu3+的5D0-7FJ(J=1,2,3,4)跃迁,这表明,在空气气氛中,部分Eu3+在Ba1.97-yZn1-xMgxSi2O7基质中被还原成了Eu2+;当x=0.1时,荧光粉Ba1.97Zn0.9Mg0.1Si2O7∶0.03Eu的绿色发光最强,表明Eu3+被还原成Eu2+离子的程度最大。当共掺入Ce3+离子后,形成Ba1.97-yZn0.9Mg0.1Si2O7∶0.03Eu,y Ce3+荧光粉体系,其发光随着Ce3+离子浓度的增大由蓝绿区经白光区到达橙红区;发现名义组成为Ba1.96Zn0.9Mg0.1Si2O7∶0.03Eu,0.01Ce3+的荧光粉的色坐标为(0.323,0.311),接近理想白光,是一种有潜在应用价值的白光荧光粉。讨论了稀土离子在Ba2Zn0.9Mg0.1Si2O7基质中的能量传递与发光机理。 相似文献
14.
Prof. Dongjiang Yang Dr. Jian Zhao Dr. Hongwei Liu Dr. Zhanfeng Zheng Dr. Moses O. Adebajo Dr. Hongxia Wang Prof. Xiaotang Liu Prof. Hongjie Zhang Prof. Jin‐cai Zhao Prof. John Bell Prof. Huaiyong Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(16):5113-5119
Cerium ions (Ce3+) can be selectively doped into the TiO2(B) core of TiO2(B)/anatase core–shell nanofibers by means of a simple one‐pot hydrothermal treatment of a starting material of hydrogen trititanate (H2Ti3O7) nanofibers. These Ce3+ ions (≈0.202 nm) are located on the (110) lattice planes of the TiO2(B) core in tunnels (width≈0.297 nm). The introduction of Ce3+ ions reduces the defects of the TiO2(B) core by inhibiting the faster growth of (110) lattice planes. More importantly, the redox potential of the Ce3+/Ce4+ couple (E°(Ce3+/Ce4+)=1.715 V versus the normal hydrogen electrode) is more negative than the valence band of TiO2(B). Therefore, once the Ce3+‐doped nanofibers are irradiated by UV light, the doped Ce3+ ions—in close vicinity to the interface between the TiO2(B) core and anatase nanoshell—can efficiently trap the photogenerated holes. This facilitates the migration of holes from the anatase shell and leaves more photogenerated electrons in the anatase nanoshell, which results in a highly efficient separation of photogenerated charges in the anatase nanoshell. Hence, this enhanced charge‐separation mechanism accelerates dye degradation and alcohol oxidation processes. The one‐pot treatment doping strategy is also used to selectively dope other metal ions with variable oxidation states such as Co2+/3+ and Cu+/2+ ions. The doping substantially improves the photocatalytic activity of the mixed‐phase nanofibers. In contrast, the doping of ions with an invariable oxidation state, such as Zn2+, Ca2+, or Mg2+, does not enhance the photoactivity of the mixed‐phase nanofibers as the ions could not trap the photogenerated holes. 相似文献
15.
Single crystals of Nd5(AsO3)4Cl3 (monoclinic, P2/n, Z = 2, a = 1026.0(1), b = 543.35(3), c = 1400.2(1) pm, β = 93.48(1)°) were obtained from the reaction of Nd2O3, As2O3 and NaCl in a sealed silica ampoule. In the crystal structure the Nd3+ ions are linked by AsO33? groups into layers that alternate with layers of Cl? ions. Two of the three crystallographically different Nd3+ ions are coordinated by eight oxygen atoms, the third one has four oxygen and four chlorine atoms as neighbours. 相似文献
16.
A novel organic-inorganic hybrid compound {[Cu(2,2′-bpy)2]2Mo8O26} has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. The compound crystallizes in the orthorhombic space group, Pna21,with a=2.4164(5),b=1.8281(4),c=1.1877(2)nm,V=5.247(2)nm^3,Z=4,and final R1=0.0331,wR2=0.0727.The structure consists of discrete {[Cu(2,2′-bpy)2]2Mo8O26} clusters,constructed from a β-octamolybdate subunit[Mo8O26]^4- covalently bonded to two [Cu(2,2′-bpy)2]^2 coordination complex cations via bridging oxo groups.In addition,the spectroscopic properties and thernal behavior of this compound have been investigated by spectroscopic techniques (UV-vis,IR,Raman and EPR spectra) and TG analysis. 相似文献
17.
《无机化学与普通化学杂志》2018,644(4):205-214
Blue single crystals of Cu[μ3‐O3P(CH2)2COOH] · 2H2O ( 1 ) and Cu[(RS)‐μ3‐O3PCH(C2H5)COOH] · 3H2O ( 2 ) were prepared in aqueous solutions (pH = 2.5–3.5). 1 crystallizes in space group Pbca (no. 61) with a = 812.5(2), b = 919.00(9), and c = 2102.3(2) pm. Cu2+ is fivefold coordinated by three oxygen atoms stemming from [O3P(CH2)2COOH]2– anions and two water molecules. The Cu–O bond lengths range from 194.0(3) to 231.8(4) pm. The connection between the [O3P(CH2)2COOH]2– anions and the Cu2+ cations yields a polymeric structure with layers parallel to (001). The layers are linked by hydrogen bonds. 2 crystallizes in space group Pbca (no. 61) with a = 1007.17(14), b = 961.2(3), c = 2180.9(4) pm. The copper cations are surrounded by five oxygen atoms in a square pyramidal fashion with Cu–O bonds between 193.6(4) and 236.9(4) pm. The coordination between [O3PCH(C2H5)COOH]2– and Cu2+ results in infinite puckered layers parallel to (001). The layers are not connected by any hydrogen bonds. Each layer contains both R and S isomers of the [O3PCH(C2H5)COOH]2– dianion. Water molecules not bound to Cu2+ are intercalated between the layers. UV/Vis spectra suggest three d–d transition bands at 743, 892, 1016 nm for 1 and four bands at 741, 838, 957, and 1151 nm for 2 , respectively. Magnetic measurements suggest a weak antiferromagnetic coupling between Cu2+ due to a super‐superexchange interaction. Thermoanalytical investigations in air show that the compounds are stable up to 95 °C ( 1 ) and 65 °C ( 2 ), respectively. 相似文献
18.
La2O(CN2)2 was synthesized from a 1:1:2 molar reaction mixture of LaCl3, LaOCl, and Li2(CN2) at 650 °C. Well developed single crystals were grown from a LiCl‐KCl flux. The crystal structure was refined as monoclinic (space group C2/c, Z = 2, a = 13.530(2) Å, b = 6.250(1) Å, c = 6.1017(9) Å, β = 104.81(2)°) from single crystal X‐ray diffraction data. The La3+ and (CN2)2— ions in the crystal structure of La2O(CN2)2 can be compared to Fe3+ and S22— ions in the cubic pyrite structure, being arranged like in a distorted NaCl type structure with their centers of gravity. In addition, the O2— ions in La2O(CN2)2 are occupying 1/4 of the tetrahedral voids formed by the arrangement of metal ions. 相似文献
19.
Crystal Structure Investigations and Thermal Behavior of the Five‐Leg Spin Ladder Compound La8Cu7O19
Barbara Schüpp Chinnathambi Sekar Wolfgang Gruner Gudrun Auffermann Carsten Bhtz Gernot Krabbes 《无机化学与普通化学杂志》2004,630(5):663-668
La8Cu7O19 was synthesized by solid state reaction of the oxides La2O3 and CuO at 1288 K in air. The crystal structure was determined by a joint Rietveld refinement of X‐ray and neutron powder diffraction data. La8Cu7O19 crystallizes in the monoclinic space group C2/c (No. 15) with the lattice parameters a = 13.8310(4)Å, b = 3.75827(9)Å, c = 34.5917(8)Å and β = 99.332(2)°. La8Cu7O19 is the n = 3 member of the homologous series La4+4nCu8+2nO14+8n. The Cu—O sub‐structure in La8Cu7O19 contains infinite ribbons, which can be described as perovskite type layers with a width of n = 3 Jahn‐Teller‐elongated octahedra, and Cu—O planes of complex geometry. DSC/TG‐measurements in different gas atmospheres show peritectic decomposition of La8Cu7O19. The anisotropic thermal expansion of the lattice parameters was investigated using synchrotron radiation. The Madelung part of lattice energy was calculated and compared with the corresponding values of other lanthanum cuprates. 相似文献
20.
Structural Chemistry and Impedance Spectroscopy of Mg2+ stabilized Na+/Pr3+-β″-Aluminas The structure with the ionic distribution in the conduction planes of a Pr3+-exchanged Mg2+ stabilized Na+-β″-alumina crystal, composition determined by electron microprobe analysis to Na1.19Pr0.13Mg0.49Al10.49O17 (degree of exchange ξ = 25%, related to Na+ content), has been investigated by single crystal X-ray diffraction methods at room temperature (R3 m, Z = 3, a = 561.8(2) pm, c = 3 361.5(11) pm). Pr3+ is slightly shifted in the ab-plane from the centrosymmetric 9 d (mO) into a 18 h site. Na+ occupies 18 h as well as 6 c (BR) positions. Ionic conductivity data of Mg2+ stabilized Na+/Pr3+-β″-Al2O3 crystals with varying degree of exchange determined by impedance spectroscopy are given in an Arrhenius diagram. With growing Pr3+ content the conductivity σ decreases with increasing activation energy. 相似文献