Structural changes induced by cation ordering in ferrotapiolite

2006 ◽  
Vol 70 (3) ◽  
pp. 319-328 ◽  
Author(s):  
M. Zema ◽  
S.C. Tarantino ◽  
A. Giorgiani
Keyword(s):  
Structural Changes ◽  
Rapid Determination ◽  
Linear Increase ◽  
X Ray Diffraction ◽  
Ionic Radii ◽  
Structural Modifications ◽  
Lattice Constants ◽  
Structure Factors ◽  
Polyhedral Volumes ◽  
Degree Of Order

AbstractStructural modifications as a function of the degree of order (Q) in FeTa2O6 ferrotapiolite have been characterized by means of single-crystal X-ray diffraction (SC-XRD). A total of 26 datasets covering the range of Q between 0.154 and 1 have been obtained by thermal treatments followed by quenching of natural tapiolite crystals. Ordering of Fe2+ at the A sites and of Ta5+ at the B sites causes a linear increase in the a/c lattice constants ratio, as a consequence of a linear decrease of the c dimension and only slight modifications of the a parameter. Calibration of a/c vs. Q represents a very useful tool for a rapid determination of the degree of order of tapiolite samples. Polyhedral volumes of the two octahedral sites vary linearly with Q as a consequence of the different ionic radii of the two species. Both the sites remain almost regular at all Q values but the B site shows an increasing off-centre displacement of the cation with increasing Q. Observed structure factors of supercell reflections, characterized by l ≠ 3n, increase linearly as a function of Q, thus representing a further tool for a quick evaluation of the degree of order.

Structural Modifications in Thin Films Caused by Gamma Radiation

2005 ◽  
Vol 480-481 ◽  
pp. 13-20 ◽  
Author(s):  
Khalil Arshak ◽  
Olga Korostynska ◽  
John Henry
Keyword(s):  
Thin Films ◽  
Gamma Radiation ◽  
Structural Changes ◽  
X Ray Diffraction ◽  
Thermal Vacuum ◽  
X Ray ◽  
Structural Modifications ◽  
Thin Oxide Films ◽  
Radiation Induced ◽  
Induced Changes

This paper reports on the gamma radiation-induced changes in thin oxide films deposited by thermal vacuum technique. Structures of various oxides thin films, such as In2O3, SiO and TeO2 and their mixtures in different proportions were studied. The influence of gamma radiation on In2O3/SiO films has resulted in significant changes in the microstructure of this film. Some kind of agglomerations with variable sizes in the range 0.5-3 µm has occurred. After a dose of 8160 µSv an evidence of partial crystallisation was observed with X-ray diffraction. Structural changes in TeO2 thin film were explored by means of Raman spectroscopy. After they have been exposed to g- radiation, a strong peak appeared at 448.83 cm-1, indicating further transformation to g-TeO2 modification.

EFFECT OF GAMMA IRRADIATION ON YBa2Cu3O7-δ HIGH TEMPERATURE SUPERCONDUCTORS

2008 ◽  
Vol 22 (27) ◽  
pp. 2699-2707 ◽  
Author(s):  
SAADAT A. SIDDIQI ◽  
RABIA SIDDIQUI ◽  
SALAMAT ALI
Keyword(s):  
Gamma Irradiation ◽  
Structural Changes ◽  
High Temperature Superconductors ◽  
Secondary Phase ◽  
Xrd Analysis ◽  
Theoretical Explanation ◽  
X Ray Diffraction ◽  
Lattice Constants ◽  
Xrd Patterns ◽  
Experimental Findings

Samples of YBa 2 Cu 3 O 7-δ superconducting ceramic were prepared and characterized by resistivity measurements using the four probe method and structural analysis using X-ray diffraction (XRD). XRD-patterns show the presence of orthorhombic Y -123 phase with a small fraction of secondary phase, YBa 2 Cu 3 O 5. Samples were irradiated with gamma (γ) rays using Co 60 source with five successive doses of 2.5 Mrad. A monotonic increase in the Tc0 value was observed for radiation dosage up to 10 Mrad. When exposed to even higher γ-doses, the Tc0 value leveled off at a saturation value or decreased. XRD-analysis shows slightly changed values of the lattice constants and a mild shift of diffraction peaks towards a lower 2θ value. These observations indicate structural changes in YBa 2 Cu 3 O 7-δ induced upon gamma irradiation. The present work describes our experimental findings and attempts to offer a theoretical explanation for the effects observed.

scholarly journals Synthesis of bioactive materials for implants in the system Ca3(PO4)2-Ca2GeO4

2018 ◽  
Vol 226 ◽  
pp. 03011
Author(s):  
Elizaveta A. Mukhanova ◽  
Vyacheslav G. Vetokhin ◽  
Alexander A. Rybalkin
Keyword(s):  
Structural Changes ◽  
Solid Phase ◽  
Calcium Phosphates ◽  
Synthesis Method ◽  
Synthesis Process ◽  
X Ray Diffraction ◽  
Bioactive Materials ◽  
Structural Modifications ◽  
Co Precipitation ◽  
Model Fluids

Various modifications of Ge-substituted calcium phosphates were obtained using solid-phase synthesis, co-precipitation in solution, and combustion synthesis. Structural changes in the synthesis process are established using X-ray diffraction. The biological activity of the obtained samples in model fluids was estimated. It has been found that the synthesis method can lead to various structural modifications of calcium phosphate, which is a significant refinement to the phase diagram of the Ca3(PO4)2- Ca2GeO4 system described in the literature.

Combined Effects of Gamma-Ray Radiation and Repeated Hot-then-Cold Stresses on the Springback Degradation in Invar Alloy

2012 ◽  
Vol 248 ◽  
pp. 14-19
Author(s):  
Cheng Fu Yang ◽  
Wei Wen Wang ◽  
Hsin Hwa Chen ◽  
Chih Hung Chu ◽  
Wei Tan Sun ◽  
...  
Keyword(s):  
Cold Stress ◽  
Structural Changes ◽  
Gamma Ray ◽  
Xrd Analysis ◽  
Linear Increase ◽  
X Ray Diffraction ◽  
Radiation Induced ◽  
Gamma Ray Irradiation ◽  
Stress Cycles ◽  
Induced Defects

In this paper, we report the characterization of springback degradation of an Invar sheet with a combination of gamma-ray irradiation and repeated hot-then-cold stresses. The springback factor value of fresh Invar without radiation shows a linear increase with the number of hot-then-cold stress cycles. Continuous springback degradations are observed as the number of hot-then-cold stress cycles reaches 100. When the Invar sheet is subjected to gamma-ray irradiation, the springback factor is greater than that of the repeated hot-then-cold stressed samples. After applying the repeated hot-then-cold stresses to the post-irradiated Invar sheets, the springback factors are first restored to the value of fresh Invar, and then revert to an increasing trend. Our previous X-ray diffraction (XRD) analysis excluded the crystalline structural changes in the post-irradiated Invar. It is believed that the radiation-induced defects, which are closely related to the springback degradation, are possibly annealed during the first 20 hot-then-cold stress cycles. These cycles ultimately dominate the springback behavior of the stressed Invar sheets.

Atomic Structure of Rare Earth Si-Al-O-N Glasses

1998 ◽  
Vol 53 (5) ◽  
pp. 259-264 ◽  
Author(s):  
H. Uhlig ◽  
M.-J. Hoffmann ◽  
S. Steeb
Keyword(s):  
Rare Earth ◽  
Neutron Diffraction ◽  
Atomic Structure ◽  
Pair Correlation ◽  
X Ray Diffraction ◽  
Ionic Radii ◽  
X Ray ◽  
Structure Factors ◽  
Total Structure

Abstract In this paper the results of X-ray diffraction experiments of Ln-Si-Al-O-N (Ln = La, Gd, Yb) glasses are presented. Total structure factors and pair correlation functions allow the determination of the first coordination sphere of Ln atoms. The bond lengths observed correspond to the ionic radii of the Ln-ions surrounded by oxygen and nitrogen atoms. The presence of non-bridging nitrogen is discussed together with results of neutron diffraction, NMR-experiments and XPS-studies of other authors.

scholarly journals Identification of patterns in diffraction intensities affected by radiation exposure

2012 ◽  
Vol 20 (1) ◽  
pp. 37-48 ◽  
Author(s):  
Dominika Borek ◽  
Zbigniew Dauter ◽  
Zbyszek Otwinowski
Keyword(s):  
Structural Changes ◽  
X Ray Diffraction ◽  
Factors Affecting ◽  
X Ray ◽  
Structure Of Molecules ◽  
Structure Factors ◽  
Unique Reflection ◽  
Radiation Induced ◽  
Value Decomposition ◽  
Induced Changes

In an X-ray diffraction experiment, the structure of molecules and the crystal lattice changes owing to chemical reactions and physical processes induced by the absorption of X-ray photons. These structural changes alter structure factors, affecting the scaling and merging of data collected at different absorbed doses. Many crystallographic procedures rely on the analysis of consistency between symmetry-equivalent reflections, so failure to account for the drift of their intensities hinders the structure solution and the interpretation of structural results. The building of a conceptual model of radiation-induced changes in macromolecular crystals is the first step in the process of correcting for radiation-induced inconsistencies in diffraction data. Here the complexity of radiation-induced changes in real and reciprocal space is analysed using matrix singular value decomposition applied to multiple complete datasets obtained from single crystals. The model consists of a resolution-dependent decay correction and a uniform-per-unique-reflection term modelling specific radiation-induced changes. This model is typically sufficient to explain radiation-induced effects observed in diffraction intensities. This analysis will guide the parameterization of the model, enabling its use in subsequent crystallographic calculations.

HRTEM Study of a Modulated Structure in Homologous Compounds In2O3(ZnO)m

1997 ◽  
Vol 3 (S2) ◽  
pp. 721-722
Author(s):  
Yoshio Bando ◽  
Chunfei Li ◽  
Masaki Nakamura ◽  
Noboru Kimizuka
Keyword(s):  
Room Temperature ◽  
Structural Changes ◽  
X Ray Diffraction ◽  
Ionic Radii ◽  
Modulated Structure ◽  
Sinusoidal Modulation ◽  
X Ray ◽  
Metal Atoms ◽  
Homologous Compounds ◽  
Random Fashion

The structure of the homologous compounds InMO3(ZnO)m (M=In, Fe, Ga, and Al, m=integer) is considered to be a layered structure, consisting of InO21− layer (In-O) ) interleaved with MZnmOm+11+ layers (M/Zn-O) along the c-axis. In the M/Zn-O layers, the distribution of two kinds of metal atoms is considered to be random fashion from X-ray diffraction analysis. However, in the previous HRTEM study of InFeO3(ZnO)m with m larger than 6, we found a modulated structure, where the image contrast showed a sinusoidal modulation curve present only in the Fe/Zn-O layers. Elemental analysis by EDS clarified that the modulated structure was caused by the ordering of Fe atoms within the Fe/Zn-O layers. In the present study, we try to observe In2O3(ZnO)m compounds, where Fe3+ atoms are replaced by In3+ atoms which have larger ionic radii. We are interested in whether the replacement of Fe3+ by In3+ atoms may cause any structural changes between In2O3(ZnO)m and InFeO3(ZnO)m.The samples were prepared by heating powders of In2O3 and ZnO sealed in Pt tube at 1350 °C for about 3 days and then rapidly cooled down to room temperature. The electron microscope observation was performed by using JEM-2000EX, operated at an accelerating voltage of 200 kV.

Isomorphous replacement in electron diffraction of wet crystals of rat hemoglobin

1983 ◽  
Vol 41 ◽  
pp. 446-447
Author(s):  
William F. Tivol ◽  
Murray Vernon King ◽  
D. F. Parsons
Keyword(s):  
Electron Diffraction ◽  
Heavy Atom ◽  
Isomorphous Substitution ◽  
X Ray Diffraction ◽  
Salt Solutions ◽  
X Ray ◽  
Isomorphous Replacement ◽  
Structure Factors ◽  
Diffraction Structure ◽  
The Mean

Feasibility of isomorphous substitution in electron diffraction is supported by a calculation of the mean alteration of the electron-diffraction structure factors for hemoglobin crystals caused by substituting two mercury atoms per molecule, following Green, Ingram & Perutz, but with allowance for the proportionality of f to Z3/4 for electron diffraction. This yields a mean net change in F of 12.5%, as contrasted with 22.8% for x-ray diffraction.Use of the hydration chamber in electron diffraction opens prospects for examining many proteins that yield only very thin crystals not suitable for x-ray diffraction. Examination in the wet state avoids treatments that could cause translocation of the heavy-atom labels or distortion of the crystal. Combined with low-fluence techniques, it enables study of the protein in a state as close to native as possible.We have undertaken a study of crystals of rat hemoglobin by electron diffraction in the wet state. Rat hemoglobin offers a certain advantage for hydration-chamber work over other hemoglobins in that it can be crystallized from distilled water instead of salt solutions.

Highlights in the history of X-ray topography1

1995 ◽  
Vol 210 (6) ◽  
Author(s):  
A. R. Lang
Keyword(s):  
Magnetic Domain ◽  
Diffraction Theory ◽  
Dislocation Loops ◽  
X Ray Diffraction ◽  
X Ray ◽  
Domain Structures ◽  
Structure Factors ◽  
History Of ◽  
Dislocation Sources ◽  
Non Destructive

AbstractX-ray topography provides a non-destructive method of mapping point-by-point variations in orientation and reflecting power within crystals. The discovery, made by several workers independently, that in nearly perfect crystals it was possible to detect individual dislocations by X-ray diffraction contrast started an epoch of rapid exploitation of X-ray topography as a new, general method for assessing crystal perfection. Another discovery, that of X-ray Pendellösung, led to important theoretical developments in X-ray diffraction theory and to a new and precise method for measuring structure factors on an absolute scale. Other highlights picked out for mention are studies of Frank-Read dislocation sources, the discovery of long dislocation helices and lines of coaxial dislocation loops in aluminium, of internal magnetic domain structures in Fe-3 wt.% Si, and of stacking faults in silicon and natural diamonds.

Multi-scale Investigation of Heterogeneous Swift Heavy Ion Tracks in Stannate Pyrochlore

2021 ◽  
Author(s):  
Eric O'Quinn ◽  
Cameron Tracy ◽  
William F. Cureton ◽  
Ritesh Sachan ◽  
Joerg C. Neuefeind ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Heavy Ion ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural Modifications ◽  
Multi Scale ◽  
Ion Tracks ◽  
Swift Heavy Ion ◽  
Transmission Electron

Er2Sn2O7 pyrochlore was irradiated with swift heavy Au ions (2.2 GeV), and the induced structural modifications were systematically examined using complementary characterization techniques including transmission electron microscopy (TEM), X-ray diffraction...

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