Neutron-diffraction studies on the time dependence of the oxygen ordering inLa2NiO4.105

1995 ◽  
Vol 51 (5) ◽  
pp. 3176-3180 ◽  
Author(s):  
J. E. Lorenzo ◽  
J. M. Tranquada ◽  
D. J. Buttrey ◽  
V. Sachan
Keyword(s):  
Neutron Diffraction ◽  
Time Dependence ◽  
Oxygen Ordering

Local oxygen ordering in superconducting YBa2Cu306.4 observed by neutron diffraction

Nature ◽  
1991 ◽  
Vol 353 (6344) ◽  
pp. 542-544 ◽  
Author(s):  
Thomas Zeiske ◽  
Rainer Sonntag ◽  
Dietmar Hohlwein ◽  
Niels Hessel Andersen ◽  
Thomas Wolf
Keyword(s):  
Neutron Diffraction ◽  
Oxygen Ordering ◽  
Local Oxygen

Neutron Diffraction Studies of High TC Superconductors

1987 ◽  
Vol 99 ◽  
Author(s):  
D. G. Hinks ◽  
B. Dabrowski ◽  
K. Zhang ◽  
C. U. Segre ◽  
J. D. Jorgensen ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Complex Function ◽  
Electronic Effects ◽  
High Tc Superconductors ◽  
High Tc ◽  
Oxygen Ordering ◽  
Powder Neutron Diffraction

ABSTRACTWe have investigated the structure and composition of La2CuO4 (both pure and Sr-doped) and Nd(Ba2−xNdx)Cu3O7 using powder neutron diffraction. In La2−xSrxCuO4, Tc reacnes its maximum at x=0.15, after which vacancies are introduced in the 2D planes and superconductivity is destroyed. Superconductivity in La2CuO4 is not bulk. No evidence for nonstoichlometry in this material can be observed. In the Nd(Ba2−xNdx)Cu3O7 system, Tc is a complex function of oxygen ordering and electronic effects.

Neutron diffraction study of Pr valence and oxygen ordering in the Y1−xPrxBa2Cu3O7−δ system

1990 ◽  
Vol 166 (1-2) ◽  
pp. 191-196 ◽  
Author(s):  
J.J. Neumeier ◽  
T. Bjørnholm ◽  
M.B. Maple ◽  
J.J. Rhyne ◽  
J.A. Gotaas
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Neutron Diffraction Study ◽  
Oxygen Ordering

First observation of superstructure reflections by neutron diffraction due to oxygen ordering inYBa2Cu3O6.35

1991 ◽  
Vol 66 (11) ◽  
pp. 1497-1500 ◽  
Author(s):  
R. Sonntag ◽  
D. Hohlwein ◽  
T. Brückel ◽  
G. Collin
Keyword(s):  
Neutron Diffraction ◽  
Oxygen Ordering

Neutron-diffraction studies on liquid, glassy, and crystalline Ca0.4K0.6(NO3)1.4

1995 ◽  
Vol 73 (11-12) ◽  
pp. 748-754 ◽  
Author(s):  
E. Kartini ◽  
M. F. Collins ◽  
B. Collier ◽  
F. Mezei ◽  
E. C. Svensson
Keyword(s):  
Neutron Diffraction ◽  
Time Dependence ◽  
Crystallization Process ◽  
Growth Patterns ◽  
Main Peak ◽  
X Ray Diffraction ◽  
Crystalline Powder ◽  
X Ray ◽  
Heat Treated ◽  
Characteristic Growth

The temperature dependence of neutron diffraction by Ca0.4K0.6(NO3)1.4, in the liquid and glassy states, was measured together with the time dependence of the transformation to the crystalline states. The measurements were performed over the range of Q from 0.2 to 5.5 Å−1 (1 Å = 10−10 m) for temperatures between 300 and 573 K. On cooling, a glass was formed with a glass transition temperature of Tg = 335 K; on heating, two crystalline phases formed at 375 ± 5 K with melting points of 425 and 444 K. As the temperature increased the height of the main peak in the diffraction pattern decreased, its position shifted to lower Q, and its width increases. Each of these parameters varies linearly with temperature. The metastability of the system was exemplified by the crystallization process, which did not occur on cooling, but which did occur on first cooling to 300 K and then on heating to 375 K. The time dependence of the growth of the crystalline powder peaks shows that there are two characteristic growth patterns, with each observed peak coming from one of two compounds. We also report on studies of quenched and heat-treated Ca0.4K0.6(NO3)1.4 by thermal analysis and X-ray diffraction.

The O–C diagrams of minor planets − a new approach to modelling the rotation

1999 ◽  
Vol 173 ◽  
pp. 185-188
Author(s):  
Gy. Szabó ◽  
K. Sárneczky ◽  
L.L. Kiss
Keyword(s):  
Error Analysis ◽  
Time Dependence ◽  
Theoretical Work ◽  
Minor Planet ◽  
Minor Planets ◽  
New Approach ◽  
Preliminary Results ◽  
Ccd Observations

AbstractA widely used tool in studying quasi-monoperiodic processes is the O–C diagram. This paper deals with the application of this diagram in minor planet studies. The main difference between our approach and the classical O–C diagram is that we transform the epoch (=time) dependence into the geocentric longitude domain. We outline a rotation modelling using this modified O–C and illustrate the abilities with detailed error analysis. The primary assumption, that the monotonity and the shape of this diagram is (almost) independent of the geometry of the asteroids is discussed and tested. The monotonity enables an unambiguous distinction between the prograde and retrograde rotation, thus the four-fold (or in some cases the two-fold) ambiguities can be avoided. This turned out to be the main advantage of the O–C examination. As an extension to the theoretical work, we present some preliminary results on 1727 Mette based on new CCD observations.

Texture measurements in Al2O3 using BEKP

1994 ◽  
Vol 52 ◽  
pp. 608-609
Author(s):  
M. D. Vaudin ◽  
J. P. Cline
Keyword(s):  
Neutron Diffraction ◽  
Rapid Method ◽  
Crystallographic Orientation ◽  
Specimen Surface ◽  
X Ray Diffraction ◽  
Anisotropic Crystal ◽  
X Ray ◽  
Verification Method ◽  
Crystal Properties ◽  
Backscattered Electron

The study of preferred crystallographic orientation (texture) in ceramics is assuming greater importance as their anisotropic crystal properties are being used to advantage in an increasing number of applications. The quantification of texture by a reliable and rapid method is required. Analysis of backscattered electron Kikuchi patterns (BEKPs) can be used to provide the crystallographic orientation of as many grains as time and resources allow. The technique is relatively slow, particularly for noncubic materials, but the data are more accurate than any comparable technique when a sufficient number of grains are analyzed. Thus, BEKP is well-suited as a verification method for data obtained in faster ways, such as x-ray or neutron diffraction. We have compared texture data obtained using BEKP, x-ray diffraction and neutron diffraction. Alumina specimens displaying differing levels of axisymmetric (0001) texture normal to the specimen surface were investigated.BEKP patterns were obtained from about a hundred grains selected at random in each specimen.

A study of oxygen and vacancy ordering in YBa2Cu3O7−x

1989 ◽  
Vol 47 ◽  
pp. 164-165
Author(s):  
Y. P. Lin ◽  
A. H. O’Reilly ◽  
J. E. Greedan ◽  
M. Post
Keyword(s):  
Electron Microscopy ◽  
Neutron Diffraction ◽  
Oxygen Content ◽  
Carbon Film ◽  
Nitrogen Atmosphere ◽  
Vacancy Ordering ◽  
Powder Samples ◽  
Vacancy Chains ◽  
Chain Ordering

In the basal planes of the orthorhombic YBa2Cu3O7-X compound with x=0.07, which has a Tc of around 90K, chains of copper-oxygen are formed along the [010] direction. Previous investigations on the variation of Tc with oxygen content have shown the existence of a plateau at Tc = 60K for x=0.3 to 0.4, suggesting the presence of a separate phase. This phase has also been identified to be orthorhombic, but with a 2x superlattice along [100] of the parent structure, and the superlattice has been attributed to the formation of alternating copper-oxygen and copper-vacancy chains. In our work, we have studied the chain ordering phenomenon by electron microscopy and neutron diffraction on samples with different oxygen contents. We report here some of our electron microscopy findings for samples with x=0.4.Powder samples of YBa2Cu3O7-X were prepared by controlled re-oxidation of previously reduced material. For electron microscopy, the sample was dry ground using a mortar and pestle in a dry nitrogen atmosphere without the use of any solvent and transferred dry onto holey carbon film for examination in a Philips CM12 microscope.

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