Sulphur-selenium compounds

1969 ◽  
Vol 22 (11) ◽  
pp. 2301 ◽  
Author(s):  
CR Ailwood ◽  
PE Fielding
Keyword(s):  
Optical Absorption ◽  
Absorption Edge ◽  
Mass Spectra ◽  
Optical Transition ◽  
Optical Absorption Edge ◽  
X Ray Diffraction ◽  
Selenium Compounds ◽  
X Ray ◽  
Direct Optical Transition

The characterization of various mixtures obtained by fractional recrystallization of sulphur-selenium melts is described. Optical absorption spectra of thin films, mass spectra, and X-ray diffraction data reveal two distinct ranges of homogeneity, the break occurring at 14 at. % Se. The optical absorption edge of crystals containing less than 14 at. % Se varies linearly with composition. A direct optical transition to the conduction band of S8 and a transition due to trapped excitons are thought to contribute to the excessive width of this absorption edge.

Crystallization Process and Chemical Disorder in Flash Evaporated Amorphous Gallium Antimonide Films

1993 ◽  
Vol 321 ◽  
Author(s):  
J. H. Dias Da Silva ◽  
I. Cisneros ◽  
L. P. Cardoso
Keyword(s):  
Optical Absorption ◽  
Absorption Edge ◽  
Gallium Antimonide ◽  
Crystallization Process ◽  
Optical Absorption Edge ◽  
X Ray Diffraction ◽  
Flash Evaporation ◽  
X Ray ◽  
Local Ordering ◽  
Chemical Disorder

ABSTRACTIn this work we describe a flash evaporation system specially built to produce Amorphous films of III-V compounds and characterize GaSb films using optical, electrical and X-Ray diffraction Measurements. Changes in the composition of the GaSb samples were obtained by the use of different crucible temperatures. In such samples, consequently, the optical absorption edge and the DC electrical conductivity were Modified. The departure from stoichiometry in GaSb films is analyzed on the basis of these results which can be used as an evidence of the chemical disorder. This kind of disorder is represented by either wrong bonds or sites with different coordination.Thermal annealing with a sequence of increasing temperatures first induced detectable variations in the optical absorption edge and in the vibrational properties of the Amorphous GaSb. These variations are compatible with the GaSb local ordering and were observed by Raman scattering and infrared absorption spectra. The annealing at higher temperatures allowed the crystallization of the material confirmed by X-Ray diffraction. From these experimental results a crystallization mechanism based on the segregation of Sb excess coming from the crystallized regions toward the Amorphous tissue is proposed.

Synthesis and Characterization of Three Novel Nitrogen-containing Macrolides

2011 ◽  
Vol 66 (9) ◽  
pp. 930-934
Author(s):  
Xin Leng ◽  
Bingqin Yang ◽  
Yuanyuan Liu ◽  
Yi Xie ◽  
Jie Tong
Keyword(s):  
Nmr Spectroscopy ◽  
Hydrogen Bonds ◽  
1H Nmr Spectroscopy ◽  
Mass Spectra ◽  
Synthesis And Characterization ◽  
Stacking Interactions ◽  
X Ray Diffraction ◽  
Preparation Methods ◽  
X Ray

Three novel nitrogen-containing macrolides have been synthesized by esterification. All of them have been characterized by infrared (IR), elemental analysis, mass spectra (MS), and 1H NMR spectroscopy, and their crystal structures were determined by single-crystal X-ray diffraction. The preparation methods and the intermolecular associations based on C-H・・・O hydrogen bonds and π- π stacking interactions are discussed.

Crystallographic and spectroscopic characterization of a natural Zn-rich spinel approaching the endmember gahnite (ZnAl2O4) composition

2013 ◽  
Vol 77 (7) ◽  
pp. 2941-2953 ◽  
Author(s):  
V. D’Ippolito ◽  
G. B. Andreozzi ◽  
F. Bosi ◽  
U. Hålenius ◽  
L. Mantovani ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Spectroscopic Characterization ◽  
Structural Formula ◽  
Unit Cell Dimension ◽  
X Ray Diffraction ◽  
Crystal Chemical Analysis ◽  
X Ray ◽  
Intervalence Charge Transfer ◽  
Oxide Spinel

AbstractThe crystal chemistry of a natural, gem-quality, blue-grey Zn-rich spinel crystal from Jemaa, Kaduna State, Nigeria, was studied using electron microprobe, single-crystal X-ray diffraction, optical absorption and Raman spectroscopies. The composition of the crystal approaches the gahnite endmember (ZnAl2O4), ∼94 mol.%, with the remainder being dominated by a hercynite component (FeAl2O4). The unit-cell dimension is 8.0850(3) Å and the tetrahedral and octahedral bond distances are determined as T–O 1.9485(6) Å and M–O 1.9137(3) Å. Crystal chemical analysis resulted in the empirical structural formula T(Zn0.94Fe2+0.03Al0.03)M (Al1.96Fe2+0.03Fe3+0.01)O4, which shows Zn and Al almost fully ordered in the tetrahedrally and octahedrally coordinated T and M sites, respectively. Raman spectra obtained using the excitation of the blue 473.1 nm line of a Nd:YAG laser display three of the five Raman-active modes predicted for the general oxide spinel group of minerals. These are the Eg mode at 420.6 cm–1 and the T2g modes at 510 cm–1 and 661 cm–1, due to vibrations in the AlO6 octahedra. Optical absorption spectra recorded in the UV/VIS-NIR-MIR range 2000 29000 cm–1 show a dominant absorption band at ∼5000 cm–1 which is caused by spin-allowed electronic d–d transitions in Fe2+ located at the T sites. The blue-grey hue exhibited by the sample is mainly due to spin-forbidden electronic transitions in TFe2+ and to MFe2+ ↔MFe3+ intervalence charge transfer, and the poor saturation of the colour is due to the small concentration of Fe2+ and Fe3+.

Urbach Edge, Disorder, and Absorption On-set in a-Si:H

2005 ◽  
Vol 862 ◽  
Author(s):  
G. D. Cody
Keyword(s):  
Thin Films ◽  
Standard Model ◽  
Optical Absorption ◽  
Amorphous Silicon ◽  
Absorption Edge ◽  
Optical Characterization ◽  
Theoretical Development ◽  
Current Status ◽  
Optical Absorption Edge

AbstractThis paper presents a brief review of the research that began in the early '80s, continued through the '90s, and produced a “standard model” for the optical absorption edge of amorphous silicon. The research began as a response to the invention of a-Si:H solar cells by Carlson and Wronski at RCA laboratories in 1976, and the subsequent worldwide interest in the optical characterization of a-Si:H thin films. The immediate need was soon met, but the research continued as an effort to understand the physics of the optical absorption edge in a-Si:H, as well as to understand the differences between, and similarities to, the indirect optical absorption edge of c-Si. In this paper, we highlight the successes of this standard model, and briefly cover its experimental and theoretical development over the last 25 years. We summarize its current status, and suggest some experimental and theoretical opportunities for, and challenges to, what may now be called a standard model for the optical absorption edge of both a-Si:H and a-Ge:H.

MICROSTRUCTURAL CHARACTERIZATION OF SPIN-VALVE MULTILAYERS BY X-RAY ANOMALOUS DIFFRACTION TECHNIQUE

2001 ◽  
Vol 15 (09n10) ◽  
pp. 291-297 ◽  
Author(s):  
C. X. LIU ◽  
M. XU ◽  
G. M. LUO ◽  
T. YANG ◽  
C. C. CHAI ◽  
...  
Keyword(s):  
Absorption Edge ◽  
Spin Valve ◽  
Microstructural Characterization ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
Multilayer Systems ◽  
Anomalous Diffraction ◽  
X Ray ◽  
Atomic Scattering

It is impossible to directly analyze the microstructure of spin-valve multilayers based on Ni, Fe, Cu and Mn by a conventional X-ray diffraction technique because the lattice parameter and atomic scattering factors of them are very close. To solve this problem, we use an X-ray anomalous diffraction technique to characterize the microstructures of the [ Ni 80 Fe 20/ Fe 50 Mn 50]15 and [ Ni 80 Fe 20/ Cu ]15 superlattice systems. The results show that more diffraction peaks and higher intensity in the reflectivity profile are observed when the incident energy is close to the absorption edge of the lighter element (Mn) in [ Ni 80 Fe 20/ Fe 50 Mn 50]15 multilayer systems and to the absorption edge of the heavier element (Cu) in the [ Ni 80 Fe 20/ Cu ]15 multilayer systems. The interface and periodic structure of [ Ni 80 Fe 20/ Fe 50 Mn 50]15 are more perfect than that of the [ Ni 80 Fe 20/ Cu ]15 superlattices. The above results are discussed in this paper.

scholarly journals The effect of the concentration of alkaline activator and aging time on the structure of metakaolin based geopolymer

2020 ◽  
Vol 52 (2) ◽  
pp. 219-229
Author(s):  
Marija Ivanovic ◽  
Ljiljana Kljajevic ◽  
Jelena Gulicovski ◽  
Marijana Petkovic ◽  
Ivona Jankovic-Castvan ◽  
...  
Keyword(s):  
Aging Time ◽  
Mass Spectra ◽  
Surface Characterization ◽  
Alkali Activation ◽  
X Ray Diffraction ◽  
Structural Reorganization ◽  
X Ray ◽  
Fourier Transformation Infrared Spectroscopy ◽  
Alkaline Activator

This paper outlines the production of an inorganic polymer/geopolymer using a metakaolin by an environmental friendly, energy saving, clean technology to conserve natural environment and resources. The influence of alkali activation, i.e. different concentration of NaOH as a component of alkali activator mixture on the process of geopolymerization of metakaolin is investigated. Also, process of aging time of geopolymer is followed by several analytical methods. The structure of metakaolin and metakaolin based geopolymers and their physicochemical properties were studied using X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR) and after 28days scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) was applied for the surface characterization of the samples. A shift of the Si-O or Si-O-X (X=Al, Si, Na...) bands as the molarity of activator increasing during geopolymerization process was observed by FTIR. Mass spectra of geopolymers were characterized by MALDI TOF mass spectrometer. Structural reorganization of geopolymer samples occurs during the curing/aging in accordance with a geopolymerization mechanism.

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.

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.

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