Two-dimensional omega energy-filtered CBED on the new Zeiss EM912

1991 ◽  
Vol 49 ◽  
pp. 786-787
Author(s):  
J. Mayer ◽  
J.C.H. Spence ◽  
G. Mobus
Keyword(s):  
Materials Science ◽  
Bloch Wave ◽  
Recording Time ◽  
Image Recording ◽  
Magnetic Filter ◽  
Magnetic Imaging ◽  
Refinement Method ◽  
Pixel Image ◽  
Diffraction Patterns ◽  
Modern Analytical

The Zeiss EM912 is a new digital, side-entry, 120 kV TEM/STEM for materials science, with omega magnetic imaging energy filter. Smallest probe is 1.6 nm. We have evaluated the 912 for quantitative CBED because we believe that the zero-loss filtered diffraction pattern is the most accurately quantifiable signal of any on a modern analytical TEM/STEM instrument. A double tilt holder and W filament were used. The magnetic filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient parallel (area) detection. Comparisons with FEG STEM instruments depend on field of view - for a 103X103 pixel image, recording time with the Omega filter using LaB6 is 1000 times less than that of a STEM with a FEG (103 times brighter) for the same dose. For accurate measurement of structure-factor amplitudes and phases, elastic energy-filtered data must be used. This Bloch-wave refinement method has now been automated using "Simplex" multivariate analysis.

Electron spectroscopic imaging and diffraction

1991 ◽  
Vol 49 ◽  
pp. 706-707
Author(s):  
M. Rühle ◽  
J. Mayer ◽  
J.C.H. Spence ◽  
J. Bihr ◽  
W. Probst ◽  
...  
Keyword(s):  
Materials Science ◽  
Electron Spectroscopic Imaging ◽  
Magnetic Filter ◽  
Magnetic Imaging ◽  
Illumination System ◽  
Probe Size ◽  
Diffraction Patterns ◽  
Fritz Haber ◽  
Koehler Illumination ◽  
First Time

A new Zeiss TEM with an imaging Omega filter is a fully digitized, side-entry, 120 kV TEM/STEM instrument for materials science. The machine possesses an Omega magnetic imaging energy filter (see Fig. 1) placed between the third and fourth projector lens. Lanio designed the filter and a prototype was built at the Fritz-Haber-Institut in Berlin, Germany. The imaging magnetic filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient area detection. The energy dispersion at the exit slit (Fig. 1) results in ∼ 1.5 μm/eV which allows imaging with energy windows of ≤ 10 eV. The smallest probe size of the microscope is 1.6 nm and the Koehler illumination system is used for the first time in a TEM. Serial recording of EELS spectra with a resolution < 1 eV is possible. The digital control allows X,Y,Z coordinates and tilt settings to be stored and later recalled.

Zero-loss omega-filtered REM and RHEED on the new Zeiss 912

1991 ◽  
Vol 49 ◽  
pp. 616-617
Author(s):  
J.C.H. Spence ◽  
J. Mayer
Keyword(s):  
Electron Microscopy ◽  
Materials Science ◽  
Surface States ◽  
Ccd Camera ◽  
Dark Field ◽  
Ion Pump ◽  
Magnetic Imaging ◽  
Reflection Electron Microscopy ◽  
Diffraction Patterns ◽  
Large Background

The Zeiss 912 is a new fully digital, side-entry, 120 Kv TEM/STEM instrument for materials science, fitted with an omega magnetic imaging energy filter. Pumping is by turbopump and ion pump. The magnetic imaging filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient parallel (area) detection. The energy loss intensity distribution may also be displayed on the screen, and recorded by scanning it over the PMT supplied. If a CCD camera is fitted and suitable new software developed, “parallel ELS” recording results. For large fields of view, filtered images can be recorded much more efficiently than by Scanning Reflection Electron Microscopy, and the large background of inelastic scattering removed. We have therefore evaluated the 912 for REM and RHEED applications. Causes of streaking and resonance in RHEED patterns are being studied, and a more quantitative analysis of CBRED patterns may be possible. Dark field band-gap REM imaging of surface states may also be possible.

A library of convergent-beam electron diffraction patterns

1986 ◽  
Vol 44 ◽  
pp. 688-691
Author(s):  
John F. Mansfield
Keyword(s):  
Electron Diffraction ◽  
Materials Science ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
Transmission Electron ◽  
Yield Information ◽  
Analytical Electron ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Electron Energy Loss

One of the most important advancements of the transmission electron microscopy (TEM) in recent years has been the development of the analytical electron microscope (AEM). The microanalytical capabilities of AEMs are based on the three major techniques that have been refined in the last decade or so, namely, Convergent Beam Electron Diffraction (CBED), X-ray Energy Dispersive Spectroscopy (XEDS) and Electron Energy Loss Spectroscopy (EELS). Each of these techniques can yield information on the specimen under study that is not obtainable by any other means. However, it is when they are used in concert that they are most powerful. The application of CBED in materials science is not restricted to microanalysis. However, this is the area where it is most frequently employed. It is used specifically to the identification of the lattice-type, point and space group of phases present within a sample. The addition of chemical/elemental information from XEDS or EELS spectra to the diffraction data usually allows unique identification of a phase.

Struther Arnott. 25 September 1934 — 20 April 2013

2015 ◽  
Vol 61 ◽  
pp. 5-22
Author(s):  
Sir Dai Rees
Keyword(s):  
Biological Sciences ◽  
Model Building ◽  
Molecular Model ◽  
Vice President ◽  
Dna And Rna ◽  
Vice Chancellor ◽  
Refinement Method ◽  
The Usa ◽  
Diffraction Patterns ◽  
Difference Fourier

Struther Arnott worked tirelessly as a researcher, teacher, leader and maker and implementer of policy in universities in Britain and the USA, always carrying his colleagues along with him through his infectious energy and breadth of academic enthusiasms and values. His outlook was shaped by the stimulus of a broad Scottish education that launched wide interests inside and outside science, including the history and literature of classical civilizations. His early research, with John Monteath Robertson FRS, was into structure determination by X-ray diffraction methods for single crystals, at a time when the full power of computers was just becoming realized for solution of the phase problem. With tenacity and originality, he then extended these approaches to materials that were to a greater or lesser extent disordered and even more difficult to solve because their diffraction patterns were poorer in information content. He brought many problems to definitive and detailed conclusion in a field that had been notable for solutions that were partial or vague, especially with oriented fibres of DNA and RNA but also various polysaccharides and synthetic polymers. His first approach was to use molecular model building in combination with difference Fourier analysis. This was followed later, and to even greater effect, by a computer refinement method that he developed himself and called linkedatom least-squares refinement. This has now been adopted as the standard approach by most serious centres of fibre diffraction analysis throughout the world. After the 10 years in which he consolidated his initial reputation at the Medical Research Council Biophysics Unit at King's College, London, in association with Maurice Wilkins FRS, he moved to Purdue University in the USA, first as Professor of Biology then becoming successively Head of the Department of Biological Sciences and Vice-President for Research and Dean of the Graduate School. As well as continuing his research, he contributed to the transformation of biological sciences at that university and to the development of the university's general management. He finally returned to his roots in Scotland as Principal and Vice-Chancellor of the University of St Andrews, to draw on his now formidable experience of international scholarship and institutional management, to reshape the patterns of academic life and mission to sit more happily and successfully within an environment that had become beset with conflict and change. He achieved this without disturbance to the harmony and wisdom embodied in the venerable traditions of that ancient Scottish yet cosmopolitan university.

Application of ODF to the Rietveld Profile Refinement of Polycrystalline Solid

1993 ◽  
Vol 37 ◽  
pp. 49-57
Author(s):  
C. S. Choi ◽  
E. F. Baker ◽  
J. Orosz
Keyword(s):  
Three Dimensional ◽  
Inverse Pole Figure ◽  
Orientation Distribution ◽  
Pole Density ◽  
Diffraction Profile ◽  
Refinement Method ◽  
Pole Figures ◽  
Diffraction Patterns ◽  
Characterization Of Materials ◽  
Profile Refinement

The Rietveld profile refinement method is probably the most popular technique used for the crystallographic characterization of materials including crystal structures and phase analysis, but it has been used mostly with ideal powder sample, not with textured polycrystals, because effects of strong and complex textures. Most technological materials are fabricated by using thermo-mechanical forming processes, which inevitably produce strong and complex preferential orientations of the crystallites. Consequently, the diffraction patterns of a given technological material are not unique but vary considerably with the measuring direction, with intensity variations as large as factors of hundreds, depending on the degree of texture. The texture effect on the diffraction pattern of a certain sample direction is directly proportional to the pole density of the corresponding inverse pole figure, which can be obtained from the three-dimensional orientation distribution function (ODF) of the material. The ODFs of materials with high crystal symmetry, such as cubic, hexagonal, tetragonal, and orthorhombic, can be determined quite precisely, using modern texture analysis techniques (for example, Bungel, Wenk, and Kallend et al.). The pole density distributions of the inverse pole figures can be used in the diffraction profile calculation of a highly textured sample.

Powder X-ray structural studies and reference diffraction patterns for three forms of porous aluminum terephthalate, MIL-53(A1)

2019 ◽  
Vol 34 (3) ◽  
pp. 216-226 ◽  
Author(s):  
W. Wong-Ng ◽  
H. G. Nguyen ◽  
L. Espinal ◽  
D. W. Siderius ◽  
J. A. Kaduk
Keyword(s):  
High Temperature ◽  
Metal Organic Framework ◽  
Space Group ◽  
X Ray ◽  
Porous Aluminum ◽  
Refinement Method ◽  
Three Samples ◽  
Metal Organic ◽  
A Cell ◽  
Diffraction Patterns

Powder X-ray diffraction patterns for three forms of MIL-53(Al), a metal organic framework (MOF) compound with breathing characteristics, were investigated using the Rietveld refinement method. These three samples are referred to as the MIL-53(Al)as-syn (the as synthesized sample), orthorhombic, Pnma, a = 17.064(2) Å, b = 6.6069(9) Å, c = 12.1636(13) Å, V = 1371.3(2) Å3, Z = 4), MIL-53(Al)LT-H (low-temperature hydrated phase, monoclinic P21/c, a = 19.4993(8) Å, b = 15.2347(6) Å, c = 6.5687(3) Å, β = 104.219(4) °, V = 1891.55(10) Å3, Z = 8), and MIL-53(Al)HT-D (high-temperature dehydrated phase, Imma, a = 6.6324(5) Å, b = 16.736(2) Å, c = 12.840(2), V = 1425.2(2) Å3, Z = 4). The crystal structures of the “as-syn” sample and the HT-D sample are confirmed to be the commonly adopted ones. However, the structure of the MIL-53(Al)LT-H phase is confirmed to be monoclinic with a space group of P21/c instead of the commonly accepted space group Cc, resulting in a cell volume double in size. The structure has two slightly different types of channel. The pore volumes and pore surface area were estimated to be 0.11766 (8) cm3/g and 1461.3(10) m2/g for MIL-53(Al)HT-D (high-temperature dehydrated phase), and 0.08628 (5) cm3/g and 1401.6 (10) m2/g for MIL-53(Al)as-syn phases, respectively. The powder patterns for the MIL-53(Al)as-syn and MIL-53(Al)HT-D phases are reported in this paper.

Effective Extinction Distances in Zone Axis Silicon

2000 ◽  
Vol 6 (S2) ◽  
pp. 1028-1029
Author(s):  
Z. Yu ◽  
R. R. Vanfleet ◽  
J. Silcox
Keyword(s):  
Electron Microscopy ◽  
Plane Waves ◽  
Normal Incidence ◽  
Sample Surface ◽  
Bloch Wave ◽  
Zone Axis ◽  
Image Recording ◽  
Intensity Measurements ◽  
Digital Image Recording ◽  
Convergent Beam

Many scientific questions encountered in electron microscopy require quantitative deductions from the observations. Comparisons of experimental observations with simulations are however, still relatively rare since measurements of intensity are normally difficult. In this paper we discuss the use of experimental observations of the effective extinction distances for zone axis silicon using a convergent beam STEM mode for comparison with a number of simulations. On the experimental side, the measurements were made with a STEM that provides accurate intensity measurements directly with a digital image recording system. Two theoretical schemes widely used in electron microscopy simulations, multislice simulation and Bloch-wave calculation, were employed for the simulations. In each case, both a TEM case and a STEM case were calculated for comparison.The multislice simulations were carried out using codes available from Kirkland. For the TEM case with plane waves at normal incidence on the sample surface, the unscattered (0,0) exit beam gives the Bright Field (BF) intensity.

Structure-refinement program for disordered carbons

1993 ◽  
Vol 26 (6) ◽  
pp. 827-836 ◽  
Author(s):  
H. Shi ◽  
J. N. Reimers ◽  
J. R. Dahn
Keyword(s):  
Structural Model ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Finite Size ◽  
Model Parameters ◽  
Refinement Method ◽  
The Difference ◽  
Diffraction Patterns ◽  
Optimizing Model ◽  
Average Lattice

An automated structure-refinement program has been developed for X-ray powder diffraction data collected on disordered carbons. The program minimizes the difference between the observed and calculated diffraction profiles in a least-squares sense by optimizing model parameters analogously to the popular Rietveld refinement method. Unlike the Rietveld method, which is designed for crystalline materials, this program allows the quantification of the finite size, strain and disorder present in disordered carbon fibers and cokes. For example, the structural model used includes the probability of a random translation parallel to adjacent carbon layers as a refinable parameter describing turbostratic disorder. Other parameters are used to describe finite size, fluctuations in the spacing between adjacent layers, average lattice constants, background and other important quantities. The structural model, combined with the refinement program, acceptably describes the diffraction patterns from disordered carbons such as pitch heated near 823 K, cokes, fibers, heat-treated cokes and synthetic graphite.

Application of High Spatial Resolution Electron Diffraction Techniques to the Study of Local Properties of Crystalline Solids

1994 ◽  
Vol 332 ◽  
Author(s):  
J W Steeds ◽  
X F Duan ◽  
P A Midgley ◽  
P Spellward ◽  
R Vincent
Keyword(s):  
Electron Diffraction ◽  
Spatial Resolution ◽  
Materials Science ◽  
High Spatial Resolution ◽  
High Quality ◽  
Resolution Electron ◽  
Electron Energy Loss Spectrometer ◽  
Local Properties ◽  
Diffraction Patterns ◽  
Electron Energy Loss

ABSTRACTThe addition of a Gatan imaging parallel electron-energy loss spectrometer (IPEELS) to a Hitachi HF 2000 cold field emission TEM has allowed us to produce high quality energy-filtered coherent electron diffraction patterns and electron holograms from a wide variety of materials. In this paper we review the recent achievements and make an assessment of the use of coherent electron diffraction in solving problems at high spatial resolution in materials science.

scholarly journals Crystallochemical Design of Huntite-Family Compounds

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 100 ◽  
Author(s):  
Galina Kuz’micheva ◽  
Irina Kaurova ◽  
Victor Rybakov ◽  
Vadim Podbel’skiy
Keyword(s):  
Rare Earth ◽  
Solid Solutions ◽  
Materials Science ◽  
Structural Features ◽  
Effective Option ◽  
Space Symmetry ◽  
Diffraction Patterns ◽  
Real Composition ◽  
The Rare Earth

Huntite-family nominally-pure and activated/co-activated LnM3(BO3)4 (Ln = La–Lu, Y; M = Al, Fe, Cr, Ga, Sc) compounds and their-based solid solutions are promising materials for lasers, nonlinear optics, spintronics, and photonics, which are characterized by multifunctional properties depending on a composition and crystal structure. The purpose of the work is to establish stability regions for the rare-earth orthoborates in crystallochemical coordinates (sizes of Ln and M ions) based on their real compositions and space symmetry depending on thermodynamic, kinetic, and crystallochemical factors. The use of diffraction structural techniques to study single crystals with a detailed analysis of diffraction patterns, refinement of crystallographic site occupancies (real composition), and determination of structure–composition correlations is the most efficient and effective option to achieve the purpose. This approach is applied and shown primarily for the rare-earth scandium borates having interesting structural features compared with the other orthoborates. Visualization of structures allowed to establish features of formation of phases with different compositions, to classify and systematize huntite-family compounds using crystallochemical concepts (structure and superstructure, ordering and disordering, isostructural and isotype compounds) and phenomena (isomorphism, morphotropism, polymorphism, polytypism). Particular attention is paid to methods and conditions for crystal growth, affecting a crystal real composition and symmetry. A critical analysis of literature data made it possible to formulate unsolved problems in materials science of rare-earth orthoborates, mainly scandium borates, which are distinguished by an ability to form internal and substitutional (Ln and Sc atoms), unlimited and limited solid solutions depending on the geometric factor.

Sign in / Sign up

Export Citation Format

Share Document