The Redistribution of Electrons in La1-xSrxCoO3 Induced by Distortion of CoO6 Octahedron

2013 ◽  
Vol 815 ◽  
pp. 845-853
Author(s):  
Hao Liu ◽  
Hong Guang Zhang ◽  
Yong Tao Li ◽  
Xue Guang Dong ◽  
Yuan Yuan Chen ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Local Structure ◽  
Solid State Reaction Method ◽  
Diffraction Peak ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Types ◽  
Diffraction Patterns ◽  
X Ray Absorption ◽  
Plane Diffraction

The La1-xSrxCoO3(x=0.0, 0.1, 0.2 and 0.3) samples were prepared by solid-state reaction method. The X-ray diffraction patterns show that the samples are ofR-3cspacegroup and the relative intensity of (024) plane diffraction peak increases with the increase of Sr concentration. The x-ray absorption fine structure data of Co ions can be fitted with 2 and 3 different scattering paths for the samples withx=0, 0.1 and forx=0.2 and 0.3, respectively. A new peak arises in x-ray absorption spectra of O ions. These results suggest a relationship between the variations of electron densities and local structure distortion. Both the valence band photoemission and x-ray absorption spectra indicate the existence of possible phase separation scenario that comes from the different types of Co-O bonds which coexist in one sample.

Local atomic structure in tetragonal pure ZrO2nanopowders

2010 ◽  
Vol 43 (2) ◽  
pp. 227-236 ◽  
Author(s):  
Leandro M. Acuña ◽  
Diego G. Lamas ◽  
Rodolfo O. Fuentes ◽  
Ismael O. Fábregas ◽  
Márcia C. A. Fantini ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Local Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Crystallite Sizes ◽  
Exafs Study ◽  
The Difference ◽  
X Ray Absorption ◽  
Good Agreement

The local atomic structures around the Zr atom of pure (undoped) ZrO2nanopowders with different average crystallite sizes, ranging from 7 to 40 nm, have been investigated. The nanopowders were synthesized by different wet-chemical routes, but all exhibit the high-temperature tetragonal phase stabilized at room temperature, as established by synchrotron radiation X-ray diffraction. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the local structure around the Zr atoms. Several authors have studied this system using the EXAFS technique without obtaining a good agreement between crystallographic and EXAFS data. In this work, it is shown that the local structure of ZrO2nanopowders can be described by a model consisting of two oxygen subshells (4 + 4 atoms) with different Zr—O distances, in agreement with those independently determined by X-ray diffraction. However, the EXAFS study shows that the second oxygen subshell exhibits a Debye–Waller (DW) parameter much higher than that of the first oxygen subshell, a result that cannot be explained by the crystallographic model accepted for the tetragonal phase of zirconia-based materials. However, as proposed by other authors, the difference in the DW parameters between the two oxygen subshells around the Zr atoms can be explained by the existence of oxygen displacements perpendicular to thezdirection; these mainly affect the second oxygen subshell because of the directional character of the EXAFS DW parameter, in contradiction to the crystallographic value. It is also established that this model is similar to another model having three oxygen subshells, with a 4 + 2 + 2 distribution of atoms, with only one DW parameter for all oxygen subshells. Both models are in good agreement with the crystal structure determined by X-ray diffraction experiments.

scholarly journals Preparation and Characterization of La0.8Sr0.2Ga0.8Mg0.2O3-δ Film by Electrophoretic Deposition Method

2010 ◽  
Vol 445 ◽  
pp. 86-90 ◽  
Author(s):  
Araki Toriyama ◽  
Kenichi Myoujin ◽  
Takayuki Kodera ◽  
Takashi Ogihara
Keyword(s):  
Thin Films ◽  
Electrophoretic Deposition ◽  
Ultrasonic Spray Pyrolysis ◽  
Diffraction Peak ◽  
Uniform Thickness ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ultrasonic Spray ◽  
Diffraction Patterns

La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) precursor particles were successfully prepared by ultrasonic spray pyrolysis. LSGM thin films were prepared by the electrophoretic deposition (EPD) technique using ethanol containing iodine. The LSGM films were obtained by sintering at 1300 °C for 10 h. The X-ray diffraction patterns revealed that the diffraction peak of LSGM thin films was in agreement with the perovskite structure. The LSGM films attained a uniform thickness of 10 μm.

scholarly journals A multi-method characterization of natural terrestrial birnessites

2020 ◽  
Vol 105 (6) ◽  
pp. 833-847
Author(s):  
Florence T. Ling ◽  
Jeffrey E. Post ◽  
Peter J. Heaney ◽  
Cara M. Santelli ◽  
Eugene S. Ilton ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Large Set ◽  
X Ray Diffraction ◽  
Full Spectrum ◽  
X Ray ◽  
High Concentrations ◽  
Diffraction Patterns ◽  
X Ray Absorption ◽  
Crystal Structure And Chemistry

Abstract With a focus on a large set of natural birnessites collected from terrestrial, freshwater systems, we applied and compared the capabilities of X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) to characterize crystal structure and chemistry. Using XRD, we successfully identified 3 of the 11 natural birnessite samples as hexagonal ranciéite-like phases, but the remaining samples yielded less interpretable “3-line” diffraction patterns with broad, asymmetrical peaks at d-spacings of ~7.2, ~2.4, and ~1.4 Å. EXAFS analysis suggested that many of these samples had characteristics of both triclinic and hexagonal birnessite. However, application of EXAFS to the ranciéite-like phases yielded unreasonably high concentrations of triclinic birnessite as an intergrowth, calling into question the use of synthetic hexagonal H-birnessite as an appropriate standard in the linear combination fitting of EXAFS data for natural birnessites. FTIR spectroscopy of the “3-line” birnessite samples successfully distinguished triclinic and hexagonal constituents, and analyses of peak positions suggested that natural birnessites occur as a full spectrum of triclinic and hexagonal intergrowths. XPS analysis of these samples revealed that higher Mn3+ concentrations relative to Mn2+ and Mn4+ are correlated to increased proportions of triclinic birnessite.

Identification of Crystalline Materials: Classification and Use of X-Ray Diffraction Patterns

1986 ◽  
Vol 1 (1) ◽  
pp. 2-6 ◽  
Author(s):  
J. D. Hanawalt ◽  
H. W. Rinn
Keyword(s):  
Theoretical Basis ◽  
X Rays ◽  
X Ray Diffraction ◽  
Crystalline Materials ◽  
X Ray ◽  
Chemical Company ◽  
The Past ◽  
Different Types ◽  
Diffraction Patterns ◽  
Or Applications

In the course of the past few years, X-ray and spectroscopic methods of analysis have found an increasing usefulness at the Dow Chemical Company. There are a large number of different types of problems on which information can be obtained by the variations of apparatus and technic which are possible in these two fields. It is not the purpose of this paper, however, to discuss these methods or applications in general, but to describe in some detail a scheme of classifying and using X-ray diffraction patterns which has been found very helpful in one particular application of X-rays — namely, that of identifying unknown substances by means of their Hull powder diffraction patterns.The inherent power of X-ray diffraction as a practical means of chemical analysis was pointed out a good many years ago. Having a different theoretical basis and depending upon an entirely different technic than other methods, it would be expected to supplement the information to be obtained from other methods and, at times, to be applicable where other methods are not suitable. It appears, however, that the use of this method has not increased at a rate commensurate with its unique and valuable features, and that it is used by relatively few academic and industrial laboratories.

Diffraction Anomalous Fine Structure: A New Technique for Probing Local Atomic Environment

1993 ◽  
Vol 307 ◽  
Author(s):  
Ingrid J. Pickering ◽  
Michael Sansone ◽  
James Marsch ◽  
Graham N. George
Keyword(s):  
Fine Structure ◽  
Absorption Edge ◽  
Short Range ◽  
Structural Information ◽  
Diffraction Peak ◽  
X Ray Diffraction ◽  
Absorbance Spectrum ◽  
X Ray ◽  
A New Technique ◽  
X Ray Absorption

ABSTRACTDiffraction anomalous fine structure (DAFS) is the fine structure in the intensity of an X-ray diffraction peak in the vicinity of an absorption edge. DAFS is measured by monitoring the intensity of a diffraction peak as a function of the incident X-ray energy as it is scanned through an absorption edge. It combines the short range structural sensitivity of X-ray absorption spectroscopy with the long range periodicity of X-ray diffraction, and can provide structural information which is not available from these techniques alone, or in combination. We present a methodology which allows extraction of a specific X-ray absorbance spectrum from the DAFS spectrum, and illustrate it for KMnO4. We also demonstrate the ability of DAFS to separate the contributions to the X-ray absorption spectrum of the tetrahedral and octahedral cobalt sites in the spinel Co3O4.

Polarized X-ray absorption spectra of Langmuir-Blodgett films: Local structure studies of merocyanine dyes

1985 ◽  
Vol 133 (1-4) ◽  
pp. 181-188 ◽  
Author(s):  
Hiroyuki Oyanagi ◽  
Michio Sugi ◽  
Shin-Ichi Kuroda ◽  
Sigeru Iizima ◽  
Takehiko Ishiguro ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Local Structure ◽  
X Ray ◽  
Langmuir Blodgett ◽  
Langmuir Blodgett Films ◽  
Merocyanine Dyes ◽  
X Ray Absorption

scholarly journals Enhanced fluorescence of selected cationic dyes adsorbed on reduced-charge montmorillonite

Clay Minerals ◽  
2011 ◽  
Vol 46 (1) ◽  
pp. 93-103 ◽  
Author(s):  
P. Pustková ◽  
Z. Klika ◽  
J. Preclíková ◽  
T. M. Grygar
Keyword(s):  
Methylene Blue ◽  
Aqueous Solutions ◽  
Absorption Spectra ◽  
Nile Blue ◽  
Cationic Dyes ◽  
X Ray Diffraction ◽  
Enhanced Fluorescence ◽  
Visible Absorption ◽  
X Ray ◽  
Diffraction Patterns

AbstractThe aggregation of three cationic dyes (CD), crystal violet (CV), Nile blue (NB) and rhodamine B (RB) in aqueous solution was studied by visible absorption spectrophotometry and compared with methylene blue (MB). The distribution of the dye species (monomers, dimers, trimers, and tetramers) in aqueous solutions with different concentrations of dye was calculated using equilibrium stepwise aggregation constants Kn. These cationic dyes were intercalated into montmorillonite (SAz-1) and its reduced charge form (RC-SAz(210)) prepared by heating lithium montmorillonite (Li/SAz-1) at 210ºC. The fluorescence of fully saturated CD/SAz and low-CD loaded CD/RC-SAz(210) complexes was studied. Visible absorption spectra of CD aqueous solutions and visible absorption spectra and X-ray diffraction patterns (d001) of the CD/SAz and CD/RC-SAz( 210) solid complexes were obtained and evaluated. Large fluorescence intensities were found for CV/RC-SAz(210) and NB/RC-SAz(210) complexes in the same way as for the complex of methylene blue with reduced-charge montmorillonite MB/RCM(210) described previously.

Sign in / Sign up

Export Citation Format

Share Document