Microstructure and crystal symmetry of Pb2Sr2(Y/Ca)Cu3O9−δ

1990 ◽  
Vol 48 (4) ◽  
pp. 64-65
Author(s):  
Y. P. Lin ◽  
J. S. Xue ◽  
J. E. Greedan
Keyword(s):  
Electron Diffraction ◽  
High Temperature Superconductors ◽  
Carbon Film ◽  
Basic Structure ◽  
Crystal Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Groups ◽  
New Family ◽  
Convergent Beam

A new family of high temperature superconductors based on Pb2Sr2YCu3O9−δ has recently been reported. One method of improving Tc has been to replace Y partially with Ca. Although the basic structure of this type of superconductors is known, the detailed structure is still unclear, and various space groups has been proposed. In our work, crystals of Pb2Sr2YCu3O9−δ with dimensions up to 1 × 1 × 0.25.mm and with Tc of 84 K have been grown and their superconducting properties described. The defects and crystal symmetry have been investigated using electron microscopy performed on crushed crystals supported on a holey carbon film.Electron diffraction confirmed x-ray diffraction results which showed that the crystals are primitive orthorhombic with a=0.5383, b=0.5423 and c=1.5765 nm. Convergent Beam Electron Diffraction (CBED) patterns for the and axes are shown in Figs. 1 and 2 respectively.

Determination of crystal symmetry for Bi4Ti3O12-based ferroelectrics by using electron diffraction

2013 ◽  
Vol 46 (3) ◽  
pp. 798-800 ◽  
Author(s):  
Wanneng Ye ◽  
Chaojing Lu ◽  
Peng You ◽  
Kun Liang ◽  
Yichun Zhou
Keyword(s):  
Electron Diffraction ◽  
Room Temperature ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Space Groups ◽  
Electron Diffraction Technique ◽  
Convergent Beam

In recent years, inconsistent space groups of monoclinicB1a1 and orthorhombicB2cbhave been reported for the room-temperature ferroelectric phases of both Bi4Ti3O12and lanthanide-substituted Bi4Ti3O12. In this article, the electron diffraction technique is employed to unambiguously clarify the crystal symmetries of ferroelectric Bi4Ti3O12and Bi3.15Nd0.85Ti3O12single crystals at room temperature. All the reflections observed from the two crystals match well with those derived fromB1a1, but the observed reflections 010, 030, {\overline 2}10 and {\overline 2}30 should be forbidden in the case ofB2cb. This fact indicates that both the ferroelectrics are of the space groupB1a1 rather thanB2cb, which is confirmed by convergent-beam electron diffraction observations. On the basis of the monoclinic space groupB1a1, the lattice parameters of both the ferroelectrics were calculated by the Rietveld refinement of powder X-ray diffraction data.

Comparison of Simulated and Experimental Order Parameters in FePt—II

2011 ◽  
Vol 17 (3) ◽  
pp. 403-409 ◽  
Author(s):  
Karen L. Torres ◽  
Richard R. Vanfleet ◽  
Gregory B. Thompson
Keyword(s):  
Electron Diffraction ◽  
Order Parameter ◽  
Convergent Beam Electron Diffraction ◽  
Order Parameters ◽  
X Ray Diffraction ◽  
Chemical Order ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Convergent Beam ◽  
Good Agreement

AbstractEight FePt thin film specimens of various thicknesses, compositions, and order parameters have been analyzed to determine the robustness and fidelity of multislice simulations in determining the chemical order parameter via electron diffraction (ED). The shape of the simulated curves depends significantly on the orientation and thickness of the specimen. The ED results are compared to kinematical scattering order parameters, from the same films, acquired from synchrotron X-ray diffraction (XRD). For the specimens analyzed with convergent beam electron diffraction conditions, the order parameter closely matched the order parameter as determined by the XRD methodology. However, the specimens analyzed by selected area electron diffraction conditions did not show good agreement. This has been attributed to substrate effects that hindered the ability to accurately quantify the intensity values of the superlattice and fundamental reflections.

A complex pseudo-decagonal quasicrystal approximant, Al37(Co,Ni)15.5, solved by rotation electron diffraction

2014 ◽  
Vol 47 (1) ◽  
pp. 215-221 ◽  
Author(s):  
Devinder Singh ◽  
Yifeng Yun ◽  
Wei Wan ◽  
Benjamin Grushko ◽  
Xiaodong Zou ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Three Dimensional ◽  
Basic Structure ◽  
Electron Diffraction Data ◽  
Dimensional Electron ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns

Electron diffraction is a complementary technique to single-crystal X-ray diffraction and powder X-ray diffraction for structure solution of unknown crystals. Crystals too small to be studied by single-crystal X-ray diffraction or too complex to be solved by powder X-ray diffraction can be studied by electron diffraction. The main drawbacks of electron diffraction have been the difficulties in collecting complete three-dimensional electron diffraction data by conventional electron diffraction methods and the very time-consuming data collection. In addition, the intensities of electron diffraction suffer from dynamical scattering. Recently, a new electron diffraction method, rotation electron diffraction (RED), was developed, which can overcome the drawbacks and reduce dynamical effects. A complete three-dimensional electron diffraction data set can be collected from a sub-micrometre-sized single crystal in less than 2 h. Here the RED method is applied forab initiostructure determination of an unknown complex intermetallic phase, the pseudo-decagonal (PD) quasicrystal approximant Al37.0(Co,Ni)15.5, denoted as PD2. RED shows that the crystal is F-centered, witha= 46.4,b= 64.6,c= 8.2 Å. However, as with other approximants in the PD series, the reflections with oddlindices are much weaker than those withleven, so it was decided to first solve the PD2 structure in the smaller, primitive unit cell. The basic structure of PD2 with unit-cell parametersa= 23.2,b= 32.3,c= 4.1 Å and space groupPnmmhas been solved in the present study. The structure withc= 8.2 Å will be taken up in the near future. The basic structure contains 55 unique atoms (17 Co/Ni and 38 Al) and is one of the most complex structures solved by electron diffraction. PD2 is built of characteristic 2 nm wheel clusters with fivefold rotational symmetry, which agrees with results from high-resolution electron microscopy images. Simulated electron diffraction patterns for the structure model are in good agreement with the experimental electron diffraction patterns obtained by RED.

scholarly journals MicroED Elucidation of Diverse Solid-State Packing in a Family of Electron-Deficient Expanded Helicenes

2020 ◽  
Author(s):  
Adrian Samkian ◽  
Gavin R. Kiel ◽  
Christopher G. Jones ◽  
Harrison Bergman ◽  
Julia Oktawiec ◽  
...  
Keyword(s):  
Solid State ◽  
Electron Diffraction ◽  
Rapid Assessment ◽  
Nanometer Scale ◽  
Proof Of Concept ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Groups ◽  
Indispensable Tool ◽  
Solid State Structures

Solid-state packing plays a defining role in the properties of a molecular organic material, but it is difficult to elucidate in the absence of single crystals that are suitable for X-ray diffraction. Here, we demonstrate the coupling of divergent synthesis with microcrystal electron diffraction (MicroED) for rapid assessment of solid-state packing motifs, using a class of chiral nanocarbons – expanded helicenes – as a proof of concept. Two highly selective oxidative dearomatizations of a readily-accessible helicene provided a divergent route to four electron-deficient analogues containing quinone or quinoxaline units. Crystallization efforts consistently yielded microcrystals that were unsuitable for single crystal X-ray diffraction, but ideal for MicroED. This technique facilitated the elucidation of solid-state structures of all five compounds with <1.1 Å resolution. The otherwise-inaccessible data revealed a range of notable packing behavior, including four different space groups, homochirality in a crystal for a helicene with an extremely low enantiomerization barrier, and nanometer scale cavities. The results of this study suggest that MicroED will soon become an indispensable tool for high-throughput investigations in pursuit of next-generation organic materials.

Measurement of Debye-Waller factors of silicon as a function of temperature using energy-filtered CBED rocking-curve technique

1994 ◽  
Vol 52 ◽  
pp. 996-997
Author(s):  
S. Swaminathan ◽  
S. Altynov ◽  
I. P. Jones ◽  
N. J. Zaluzec ◽  
D. M. Maher ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Liquid Nitrogen Temperature ◽  
Convergent Beam Electron Diffraction ◽  
Higher Order ◽  
X Ray Diffraction ◽  
Beam Electron ◽  
X Ray ◽  
Crystal Potential ◽  
Transmission Electron ◽  
Convergent Beam

The advantages of quantitative Convergent Beam Electron Diffraction (CBED) method for x-ray structure factor determination have been reviewed by Spence. The CBED method requires accurate values of Debye-Waller (D-W) factors for the estimation of the coefficients of crystal potential of the higher order beams, Vg, the calculation of the absorption potential, V′g using the Einstein model for phonons, and finally the conversion of the fitted values of the coefficients of crystal potential, V″, to x-ray structure factors. Debye-Waller factors are conventionally determined by neutron or x-ray diffraction methods. Because of the difficulties in conducting high temperature neutron and x-ray diffraction experiments, D-W factors are rarely measured at temperatures above room temperature. Debye-Waller factors at high temperatures can be determined by Convergent Beam Electron diffraction (CBED) method using Transmission Electron Microscopy (TEM) employed with a hot stage attachment. Recently Holmestad et al. have attempted to measure the D-W factors by matching the energy-filtered Higher Order Laue Zone (HOLZ) line intensities near liquid nitrogen temperature.

Relative Lattice Parameter Measurement in Quaternary (InGaAsP) Layers on InP Substrates Using Convergent Beam Electron Diffraction

1986 ◽  
Vol 69 ◽  
Author(s):  
M. E. Twigg ◽  
S. N. G. Chu ◽  
D. C. Joy ◽  
D. M. Maher ◽  
A. T. Macrander ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Lattice Parameter ◽  
Convergent Beam Electron Diffraction ◽  
X Ray Diffraction ◽  
Device Structure ◽  
Beam Electron ◽  
X Ray ◽  
Convergent Beam ◽  
Relative Change ◽  
Inp Substrates

AbstractWith X-ray diffraction techniques, it is possible to routinely measure lattice parameters to several parts in 104 for macroscopic specimens. However, measurements of lattice parameter changes for quaternary (InGaAsP) device structures several microns in width are not usually feasible with X-ray diffraction techniques. Convergent Beam Electron Diffraction (CBED), which is one of the techniques available on a modern transmission electron microscope (TEM), may be sensitive to these small, localized lattice parameter changes. Unfortunately, dynamical diffraction effects prevent direct extraction of changes in the lattice parameter from CBED patterns which are obtained from high atomic number materials. For this reason, we have chosen to calibrate the relative position of CBED features with X-ray lattice parameter measurements which were obtained from planar quaternary layers grown on InP substrates. For the active quaternary region of an electro-optical device structure, it is shown that this approach may be sensitive to a relative change in the lattice parameter as small as ±2 parts in 104, which is the uncertainty in the X-ray calibration measurements.

scholarly journals Different Polyoxometalate Structures Obtained from the Na11H[H(2-x)Bi2W20O70(HWO3)x]·46H2O(x=1.4).

2018 ◽  
Vol 1 (2) ◽  
pp. 93-100
Author(s):  
Suhair Atta
Keyword(s):  
Single Crystal ◽  
Self Assembly ◽  
Multiple Testing ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
X Ray ◽  
Space Groups ◽  
Cell Parameters ◽  
New Family ◽  
Ft Ir

In the supramolecular chemistry world, Polyoxometalates (POMs) are considered as a new family of inorganic molecular containers, construct itself by self-assembly reaction from very small units, to form a cluster with unique structural and properties. three structures reported in this paper - differ in their unit cell parameters and also differ from the well-known - as the result of reaction of the Na11H[H(2- x)Bi2W20O70(HWO3)x]·46H2O (x=1.4) with Ca ion at different pH conditions. These structures are [Ca(H2O)7]2[Na(H2O)2]2[HBi2W20O70(HWO3)].14H2O(1), H2[NH4]10[HBi2W20O70(HWO3)] (2), and [NH4]6[Na(H2O)4]2[Ca(H2O)4]2[W12O42].2H2O (3). The last one is bismuth-free and it is formed through reassembly of the precursor. Full structural characterization was made by multiple testing techniques such as single-crystal X-ray diffraction, UV-visible spectroscopy, FT-IR, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The single-crystal X-ray diffraction results for the three compounds are as follows:(1), Triclinic, space group P-1, while (2) and (3) crystallize in monoclinic space groups C2/m and P21/n respectively.

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