X-ray Diffraction and Site Preference Analysis of Ni-Substituted MgFe2O4 Ferrites

2002 ◽  
Vol 2 (12) ◽  
pp. 1110-1114 ◽  
Author(s):  
Mazhar U. rana . ◽  
Misbah-ul-Islam . ◽  
Tahir Abbas .
Keyword(s):  
Site Preference ◽  
X Ray Diffraction ◽  
Preference Analysis ◽  
X Ray

Ternary aurides RE4Mg3Au10 (RE=Y, Nd, Sm, Gd–Dy) and their silver analogues

2015 ◽  
Vol 70 (2) ◽  
pp. 135-141 ◽  
Author(s):  
Theresa Block ◽  
Michael Johnscher ◽  
Stefan Linsinger ◽  
Ute Ch. Rodewald ◽  
Rainer Pöttgen
Keyword(s):  
Three Dimensional ◽  
Intermetallic Phases ◽  
Point Of View ◽  
Site Preference ◽  
Induction Melting ◽  
X Ray Diffraction ◽  
X Ray ◽  
Synthesis Conditions ◽  
Coordination Numbers ◽  
Cation Sites

AbstractThe ternary aurides RE4Mg3Au10 (RE=Y, Nd, Sm, Gd–Dy) and their silver analogues were synthesized by induction melting of the elements in sealed niobium tubes. These intermetallic phases were characterized by powder X-ray diffraction. They crystallize with the Ca4In3Au10-type structure, which, from a geometrical point of view, is a ternary ordered version of Zr7Ni10 with the rare earth and magnesium atoms ordering on the four crystallographically independent zirconium sites. The structures of crystals from three differently prepared gadolinium samples were refined from single-crystal X-ray diffractometer data: Cmca, a=1366.69(3), b=998.07(4), c=1005.54(3) pm, wR2=0.0332, 1234 F2 values, 46 variables for Gd4.43Mg2.57Au10, a=1378.7(1), b=1005.3(1), c=1011.2(1) pm, wR2=0.0409, 1255 F2 values, 48 variables for Gd5.50Mg1.50Au10, and a=1350.2(5), b=995.5(1), c=1009.3(1) pm, wR2=0.0478, 1075 F2 values, 48 variables for Gd5.61Mg1.39Au10. All crystals show substantial Mg/Gd mixing on two sites. The gold atoms form a pronounced two-dimensional substructure with Au–Au distances of 278 to 297 pm in Gd4.43Mg2.57Au10. These gold blocks are condensed via magnesium atoms (278–315 pm Mg–Au). The gadolinium atoms fill larger cavities within the three-dimensional networks. The magnesium vs. gadolinium site preference is a consequence of the different coordination numbers of the cation sites. All phases show homogeneity ranges RE4+xMg3–xAg10 and RE4+xMg3–xAu10. The influence of the synthesis conditions is briefly discussed.

Single crystal X-ray studies of cation-deficient magnetite

1997 ◽  
Vol 212 (6) ◽  
Author(s):  
H. Okudera
Keyword(s):  
Single Crystal ◽  
Cation Vacancy ◽  
Site Preference ◽  
Mean Square ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cation Deficiency ◽  
Octahedral Cation ◽  
Synthetic Magnetite ◽  
Cation Sites

AbstractSite preference of cation vacancy and the effect of cation deficiency on the structure parameters have been investigated for synthetic magnetite specimens by means of the single-crystal X-ray diffraction methods. The cation vacancies are selectively formed at the octahedral cation sites even in the specimen quenched from 1793 K. The effects of cation deficiency are found as increase of atomic mean square displacements and decrease of anisotropy in thermal motions of the octahedral site cations.

Characterization of trace Nd and Ce site preference and coordination in natural melanites: a combined X-ray diffraction and high-energy XAFS study

2002 ◽  
Vol 29 (7) ◽  
pp. 495-502 ◽  
Author(s):  
S. Quartieri ◽  
F. Boscherini ◽  
J. Chaboy ◽  
M.C. Dalconi ◽  
R. Oberti ◽  
...  
Keyword(s):  
High Energy ◽  
Site Preference ◽  
X Ray Diffraction ◽  
X Ray

scholarly journals Preparation and Characterization of Manganese Ferrite Aluminates

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
R. L. Dhiman ◽  
S. P. Taneja ◽  
V. R. Reddy
Keyword(s):  
Mössbauer Spectra ◽  
Spinel Phase ◽  
Lattice Parameter ◽  
Aluminum Concentration ◽  
Site Preference ◽  
X Ray Diffraction ◽  
Hyperfine Fields ◽  
Ionic Radii ◽  
X Ray ◽  
Mossbauer Spectra

Aluminum doped manganese ferritesMnAlxFe2−xO4with0.0≤x≤1.0have been prepared by the double ceramic route. The formation of mixed spinel phase has been confirmed by X-ray diffraction analysis. The unit cell parameter `aO' is found to decrease linearly with aluminum concentration due to smaller ionic radius of aluminum. The cation distributions were estimated from X-ray diffraction intensities of various planes. The theoretical lattice parameter, X-ray density, oxygen positional parameter, ionic radii, jump length, and bonds and edges lengths of the tetrahedral (A) and octahedral (B) sites were determined.57Fe Mössbauer spectra recorded at room temperature were fitted with two sextets corresponding to Fe3+ions at A- and B-sites. In the present ferrite system, the area ratio of Fe3+ions at the A- and B-sites determined from the spectral analysis of Mössbauer spectra gives evidence that Al3+ions replace iron ions at B-sites. This change in the site preference reflects an abrupt change in magnetic hyperfine fields at A- and B-sites as aluminum concentration increases, which has been explained on the basis of supertransferred hyperfine field. On the basis of estimated cation distribution, it is concluded that aluminum doped manganese ferrites exhibit a 55% normal spinel structure.

Rare Earth Site Preference in the Doped Laser Host Material Sc2SiO5. A Single-Crystal X-Ray Study

2012 ◽  
Vol 67 (2) ◽  
pp. 113-117 ◽  
Author(s):  
Ute Ch. Rodewald ◽  
Lihe Zheng ◽  
Birgit Heying ◽  
Xiaodong Xu ◽  
Liangbi Su ◽  
...  
Keyword(s):  
Rare Earth ◽  
Single Crystal ◽  
Diffraction Data ◽  
Host Material ◽  
Site Preference ◽  
Czochralski Technique ◽  
X Ray Diffraction ◽  
High Quality ◽  
X Ray ◽  
Oxygen Coordination

Single crystals of the laser host material Sc2SiO5 as well as thulium- (4 at.-%) and ytterbium- (5 at.-%) doped samples were prepared by the Czochralski technique. The structures of Sc2SiO5, Tm3+:Sc2SiO5, and Yb3+:Sc2SiO5 were refined on the basis of high-quality single-crystal X-ray diffraction data: monoclinic Y2SiO5 type, space group C2/c. The X-ray data unambiguously show that the larger rare earth cations exclusively occupy the 8 f site with oxygen coordination number 7.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

Ribosome Structural Organization

1974 ◽  
Vol 32 ◽  
pp. 332-333
Author(s):  
James A. Lake
Keyword(s):  
Ribosomal Proteins ◽  
Structural Organization ◽  
Three Dimensional ◽  
Small Subunit ◽  
Structural Studies ◽  
X Ray Diffraction ◽  
Specific Antibodies ◽  
X Ray ◽  
E Coli ◽  
Complete Sequences

The understanding of ribosome structure has advanced considerably in the last several years. Biochemists have characterized the constituent proteins and rRNA's of ribosomes. Complete sequences have been determined for some ribosomal proteins and specific antibodies have been prepared against all E. coli small subunit proteins. In addition, a number of naturally occuring systems of three dimensional ribosome crystals which are suitable for structural studies have been observed in eukaryotes. Although the crystals are, in general, too small for X-ray diffraction, their size is ideal for electron microscopy.

Electron Microscopy of Human Gallstones

1971 ◽  
Vol 29 ◽  
pp. 296-297
Author(s):  
C. Wolpers ◽  
R. Blaschke
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Bile Pigment ◽  
X Ray Diffraction ◽  
Triclinic Crystal System ◽  
X Ray ◽  
Follow Up Study ◽  
Infra Red ◽  
Main Components

Scanning microscopy was used to study the surface of human gallstones and the surface of fractures. The specimens were obtained by operation, washed with water, dried at room temperature and shadowcasted with carbon and aluminum. Most of the specimens belong to patients from a series of X-ray follow-up study, examined during the last twenty years. So it was possible to evaluate approximately the age of these gallstones and to get information on the intensity of growing and solving.Cholesterol, a group of bile pigment substances and different salts of calcium, are the main components of human gallstones. By X-ray diffraction technique, infra-red spectroscopy and by chemical analysis it was demonstrated that all three components can be found in any gallstone. In the presence of water cholesterol crystallizes in pane-like plates of the triclinic crystal system.

High Resolution Replication of Organoclay Surfaces

1982 ◽  
Vol 40 ◽  
pp. 576-577
Author(s):  
W. W. Barker ◽  
W. E. Rigsby ◽  
V. J. Hurst ◽  
W. J. Humphreys
Keyword(s):  
Clay Mineral ◽  
Organic Molecule ◽  
Organic Molecules ◽  
X Ray Diffraction ◽  
Xrd Pattern ◽  
X Ray ◽  
Naturally Occurring ◽  
Silicate Layers ◽  
Mineral Identification

Experimental clay mineral-organic molecule complexes long have been known and some of them have been extensively studied by X-ray diffraction methods. The organic molecules are adsorbed onto the surfaces of the clay minerals, or intercalated between the silicate layers. Natural organo-clays also are widely recognized but generally have not been well characterized. Widely used techniques for clay mineral identification involve treatment of the sample with H2 O2 or other oxidant to destroy any associated organics. This generally simplifies and intensifies the XRD pattern of the clay residue, but helps little with the characterization of the original organoclay. Adequate techniques for the direct observation of synthetic and naturally occurring organoclays are yet to be developed.

Electron Microscopy of Shock Loaded Polycrystalline Beryllium

1974 ◽  
Vol 32 ◽  
pp. 506-507 ◽  
Author(s):  
J. M. Galbraith ◽  
L. E. Murr ◽  
A. L. Stevens
Keyword(s):  
Electron Microscopy ◽  
Wave Propagation ◽  
Structural Change ◽  
Single Crystal ◽  
Diffraction Pattern ◽  
Shock Loading ◽  
Slip Systems ◽  
Compression Tests ◽  
X Ray Diffraction ◽  
X Ray

Uniaxial compression tests and hydrostatic tests at pressures up to 27 kbars have been performed to determine operating slip systems in single crystal and polycrystal1ine beryllium. A recent study has been made of wave propagation in single crystal beryllium by shock loading to selectively activate various slip systems, and this has been followed by a study of wave propagation and spallation in textured, polycrystal1ine beryllium. An alteration in the X-ray diffraction pattern has been noted after shock loading, but this alteration has not yet been correlated with any structural change occurring during shock loading of polycrystal1ine beryllium.This study is being conducted in an effort to characterize the effects of shock loading on textured, polycrystal1ine beryllium. Samples were fabricated from a billet of Kawecki-Berylco hot pressed HP-10 beryllium.

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