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101.
The compositions in the YBa2−xLaxCu3O7−δ (0x0.2) system were prepared by the solid state reaction, employing a novel high-temperature oxygen sintering route. The modified sintering route yields dense slab like microstructures with large grains. The decomposition (incongruent melting) temperature of the YBa2Cu3O7−δ (Y-123) phase was found to shift to higher temperatures with increasing oxygen partial pressure and lanthanum content. Structure remained orthorhombic up to x=0.2 with a decrease in the orthorhombic strain ((b−a)/b). Iodometric titration indicated a systematic increase in the oxygen content with increasing lanthanum content. Thermo-gravimetric studies in various oxygen partial pressures revealed that the oxygen diffusion in to the YBa2Cu3O7−δ (δ>0.5) lattice is an exothermic event and takes place at temperatures not less than 573 K. High-temperature thermal-expansion measurements in air indicated that the nonlinearity in thermal expansion behaviour was reduced by the substitution of lanthanum. 相似文献
102.
Polyoxometalates(POMs0) containing Keggin moieties exhibit a wide variety of compositions and have considerable structrral versatility as well as important magnetic, optical,and catalytic proper-ties[1-6]. 相似文献
103.
A new class of low melting liquid crystalline octaalkyloxyporphyrins have been synthesised. Their Zn(II)-complexes display an interesting ligation behaviour towards amines (of varying shapes and sizes), ascribed to the steric hindrance or hydrophobic pockets on both the faces of the porphryin as evidenced from the crystal structure of Zn(II)-octabutyloxyporphyrin. 相似文献
104.
Formation and Crystal Structure of an Oxygen Bridged Titanium Amino Bisphenoxide Di‐(μ‐oxo)‐titan‐bis[aminobisphenoxide] ( 3 ) was obtained by reaction of (i‐Prop)2TiL* ( 2 ) {L* = O‐4, 6‐(t‐Bu)2C6H2‐2‐CH2‐[1, 4‐N2C5H10]‐2'‐CH2‐4', 6'‐(t‐Bu)2C6H2O] with water in a molar ratio 1:1 in diethylether. Both i‐Propyl moieties are substituted yielding the dimeric oxygen bridged amino bisphenoxide complex. The six coordinate Ti atoms are a result of Ti—N and Ti—O interactions of the corresponding atoms of the amino bisphenoxide ligand and the bridging O atoms. The central planar Ti2O2 ring may be considered as the general structural feature of the title compound: Space group P1¯, Z = 1, lattice dimensions at —60°C: a = 11.6899(4), b = 11.7873(4), c = 12.6462(4) Å, α = 98.070(1), β = 99.660(1), γ = 95.343(1)°, R1 = 0.0469, wR2 = 0.1049, GooF = 0.939. 相似文献
105.
106.
By reacting platinum with alkali metals (A = K, Rb, Cs) a new family of binary alkali metal platinides has been synthesized and characterized by chemical analysis, X‐ray powder diffraction, thermal analysis (DTA and DSC), and magnetic measurements. All three compounds exhibit similar XRD‐patterns with strong reflections that can be indexed on the basis of a rhombohedral crystal system (KxPt: a = 2.6462(1), c = 17.123(1); RbxPt: a = 2.6415(1) Å, c = 17.871(1) Å; CsxPt: a = 2.6505(1) Å, c = 18.536(1) Å; x < ½. The a lattice constant is independent on the alkali metal used and of value close to the Pt–Pt distance in NaPt2 (2.645Å). The c parameter increases monotonically with the growing atomic radius of the alkali metal. The average structure of the alloys consists of cubic close packed layers of platinum atoms with layers of disordered alkali metals in between. For all compounds besides the strong reflections small satellites are observed which cannot be indexed together with the rhombohedral peaks in any rational 3‐dimensional lattice. However, these satellites can be indexed as incommensurate modulations within the ab plane (found propagation vectors k = (0.1011, 0.2506, 0) for CsxPt, and k = (0.0168, 0.2785, 0) for RbxPt). 相似文献
107.
108.
以XRD法确定制得的标题晶体属空间群D_(3A)~3,a=13.111,c=11.130。结构由帕特逊-极小函数法结合差值法解出,经精修得一致性因子R_w=0.0344。晶胞中坐落在6m2特殊位置上的是包合1个Cl~-的聚十五钒酸根[V_(15)O_(36)Cl]~(10-),配合键价法确认这是四价钒占主导地位的一类特种混合价同多酸根。 相似文献
109.
The title compound (C30H27NO3) was synthesized via a one-pot procedure starting from β-benzoylthioacetanilide, benzaldehyde and 5,5-dimethyl-1,3-cyclohexanedione, and its struc- ture was determined by single-crystal X-ray diffraction analysis. The crystal belongs to triclinic system, space group P, with a = 6.325(2), b = 11.243(3), c = 17.553(4) , α = 87.306(4), β = 80.822(4), γ = 77.798(4)°, V = 1204.2(5) 3, Z = 2, Mr = 449.53, Dc = 1.240 g/cm3, μ = 0.080 mm-1, F(000) = 476, the final R = 0.0459 and wR = 0.0970 for 2301 observed reflections with I > 2σ(I). 相似文献
110.
以不同分子筛(Nonasil, MCM-22或MCM-49)为晶种, 在水热条件下以六亚甲基亚胺(HMI)为模板剂, 对纯硅沸石Nonasil(HMI)的合成进行了研究. 并且对各种合成参数, 包括晶种类型、硅源、晶化温度和Na+浓度等对Nonasil(HMI)合成的影响进行了探讨. 发现在适量的Na+存在条件下, 晶种的引入大大缩短了晶化时间; 不同类型的晶种对晶化速度有不同程度的提高. 特别是用异类晶种(如MCM-22或MCM-49)能够合成高结晶度的Nonasil(HMI). 相似文献