TEM Characterization of a Modulated β Phase in Polycrystalline Dicalcium Silicate

1991 ◽  
Vol 49 ◽  
pp. 946-947
Author(s):  
Y. J. Kim ◽  
I. Nettleship ◽  
W. M. Kriven
Keyword(s):  
Atmospheric Pressure ◽  
Imaging Techniques ◽  
Dicalcium Silicate ◽  
Temperature Range ◽  
Β Phase ◽  
Tem Characterization ◽  
Diffraction Patterns

Five polymorphs are known as major phases in pure dicalcium silicate (Ca2SiO4) at atmospheric pressure—α, α'H, α'L, β and γ. Fully dense pellets were prepared by sintering chemically prepared powders in the temperature range of 1300 to 1400°C for 1 to 12 hours. Their phases and microstructures were studied by TEM through selected area diffraction patterns (SADP's) and imaging techniques.

TEM characterization of the α' and β phases in polycrystalline distrontium silicate (Sr2SiO4)

1992 ◽  
Vol 50 (1) ◽  
pp. 354-355
Author(s):  
Y. J. Kim ◽  
J. L. Shull ◽  
W. M. Kriven
Keyword(s):  
Electron Beam ◽  
Phase Space ◽  
Atmospheric Pressure ◽  
Sintering Temperature ◽  
Major Phase ◽  
Space Group ◽  
Temperature Range ◽  
Β Phase ◽  
Tem Characterization

Two polymorphs, α' and β, are known to be major phases in pure distrontium silicate (Sr2SiO4) at atmospheric pressure. Fully dense pellets were fabricated by sintering chemically prepared powders in the temperature range of 900° to 1400°C for 1 to 5 hours. Their phases and microstructures were studied by TEM. At lower sintering temperatures such as 900°C, the major phase was orthorhombic α' (space group, Pmnb). The euhedral α' grains had a size of about 1 μm diameter (Fig. la). As the sintering temperature increased, the amount of monoclinic β phase (space group, P21/n) tended to increase. These β grains were usually irregular and twinned on {100}β or {001}β planes. Concentration of the electron beam on the grains gave rise to a disappearance of twins (Fig. lb).

TEM - characterization of precipitates in Al-Zn5-Mgl

1978 ◽  
Vol 36 (1) ◽  
pp. 638-639
Author(s):  
H.P. Degischer ◽  
W. Lacom
Keyword(s):  
Orientation Relationship ◽  
Zone Axis ◽  
Strong Interactions ◽  
Lattice Structures ◽  
Beam Direction ◽  
Cubic Lattices ◽  
Tem Characterization ◽  
The Matrix ◽  
Diffraction Patterns

Various techniques of TEM are described to investigate precipitates in metals, which reach dimensions from a few nm to more than 100 nm. The examples presented here are characterized by strong interactions of the lattice structures of the inclusions and the matrix, therefore replica techniques are not applicable (an example of that is presented in [1]] because the metastable phases might change.Selected area diffraction of regions of about 100 nm give well defined diffraction patterns of the phases present in that part of the specimen. Generally the diagram corresponding to a single precipitate cannot be obtained, but in contrast to microdiffraction techniques sharp diffraction spots can be measured. The orientation relationship between the inclusions and the matrix can be studied best, if the beam direction coincides with the main cristallographic zone axis, i.e. in cubic lattices: <001>, <112>, <111>, <011>. At these poles the patterns are highly symmetric, especially because of doublediffraction, but the diagram can be constructed to unfold the coinciding patterns.

DIELECTRIC PROPERTIES OF Zr-DOPED Ba0.985Bi0.01TiO3 SYNTHESIZED BY INORGANIC DISTILLATION UNDER ATMOSPHERIC PRESSURE

2013 ◽  
Vol 27 (04) ◽  
pp. 1350026 ◽  
Author(s):  
JING WANG ◽  
SHENGLIN JIANG ◽  
LINHUA SONG
Keyword(s):  
Atmospheric Pressure ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
Multilayer Ceramic Capacitors ◽  
X Ray ◽  
High K ◽  
Diffraction Patterns ◽  
High K Dielectric ◽  
Diffuse Phase

To meet the requirement of next-generation multilayer ceramic capacitors, the synthesis and characterization of Ba 0.985 Bi 0.01 TiO 3-based high-k dielectric compositions are reported. Solid solutions with a nominal composition of 0.4 Ba 0.985 Bi 0.01 TiO 3–0.6 BaTi 1-x Zr x O 3 (x = 0.001, 0.005, 0.01, 0.02, 0.04, 0.06, 0.1) was synthesized by distillation method. Room-temperature X-ray diffraction patterns showed an increase and then a decrease in the tetragonality of Ba 0.985 Bi 0.01 TiO 3 after modifying with BaTi 1-x Zr x O 3. The decrement in tetragonality (c/a ratio) was accompanied by lowering of Curie temperature. 0.4 Ba 0.985 Bi 0.01 TiO 3–0.6 BaTi 0.995 Zr 0.005 O 3 was found to exhibit diffuse phase transition accompanied by an ultrahigh dielectric constant of 77,619, a loss tangent < 1 and a grain size < 1 μm.

Microstructural and Microchemical Characterization of Nickel Sulfide Inclusions in Plate Glass

1991 ◽  
Vol 49 ◽  
pp. 962-963
Author(s):  
J. Cooper ◽  
O. Popoola ◽  
W. M. Kriven
Keyword(s):  
Thermal Expansion ◽  
Phase Transformation ◽  
Glass Matrix ◽  
Nickel Sulfide ◽  
Plate Glass ◽  
Thermal Expansion Mismatch ◽  
Volume Increase ◽  
Β Phase ◽  
Microchemical Characterization

Nickel sulfide inclusions have been implicated in the spontaneous fracture of large windows of tempered plate glass. Two alternative explanations for the fracture-initiating behaviour of these inclusions have been proposed: (1) the volume increase which accompanies the α to β phase transformation in stoichiometric NiS, and (2) the thermal expansion mismatch between the nickel sulfide phases and the glass matrix. The microstructure and microchemistry of the small inclusions (80 to 250 μm spheres), needed to determine the cause of fracture, have not been well characterized hitherto. The aim of this communication is to report a detailed TEM and EDS study of the inclusions.

Electron microscope characterization of MOCVD-grown gap layers on Si

1986 ◽  
Vol 44 ◽  
pp. 724-725
Author(s):  
K.M. Jones ◽  
M.M. Al-Jassim ◽  
J.M. Olson
Keyword(s):  
Atmospheric Pressure ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
Organic Chemical ◽  
Lattice Match ◽  
Si Substrates ◽  
Metal Organic ◽  
Good Lattice ◽  
Antiphase Domains

The epitaxial growth of III-V semiconductors on Si for integrated optoelectronic applications is currently of great interest. GaP, with a lattice constant close to that of Si, is an attractive buffer between Si and, for example, GaAsP. In spite of the good lattice match, the growth of device quality GaP on Si is not without difficulty. The formation of antiphase domains, the difficulty in cleaning the Si substrates prior to growth, and the poor layer morphology are some of the problems encountered. In this work, the structural perfection of GaP layers was investigated as a function of several process variables including growth rate and temperature, and Si substrate orientation. The GaP layers were grown in an atmospheric pressure metal organic chemical vapour deposition (MOCVD) system using trimethylgallium and phosphine in H2. The Si substrates orientations used were (100), 2° off (100) towards (110), (111) and (211).

Quantitative nano-characterization of heterogeneous catalysts

1995 ◽  
Vol 53 ◽  
pp. 398-399
Author(s):  
P.A. Crozier ◽  
M. Pan
Keyword(s):  
Heterogeneous Catalysts ◽  
Low Dose ◽  
Imaging Techniques ◽  
Structural Features ◽  
Catalyst Characterization ◽  
New Developments ◽  
Double Phase ◽  
Phase Systems ◽  
Dose Imaging

Heterogeneous catalysts can be of varying complexity ranging from single or double phase systems to complicated mixtures of metals and oxides with additives to help promote chemical reactions, extend the life of the catalysts, prevent poisoning etc. Although catalysis occurs on the surface of most systems, detailed descriptions of the microstructure and chemistry of catalysts can be helpful for developing an understanding of the mechanism by which a catalyst facilitates a reaction. Recent years have seen continued development and improvement of various TEM, STEM and AEM techniques for yielding information on the structure and chemistry of catalysts on the nanometer scale. Here we review some quantitative approaches to catalyst characterization that have resulted from new developments in instrumentation.HREM has been used to examine structural features of catalysts often by employing profile imaging techniques to study atomic details on the surface. Digital recording techniques employing slow-scan CCD cameras have facilitated the use of low-dose imaging in zeolite structure analysis and electron crystallography. Fig. la shows a low-dose image from SSZ-33 zeolite revealing the presence of a stacking fault.

TEM characterization of proton-exchanged LiNbO3 optical waveguides

1986 ◽  
Vol 44 ◽  
pp. 480-481
Author(s):  
W. E. Lee
Keyword(s):  
Refractive Index ◽  
Benzoic Acid ◽  
Optical Waveguides ◽  
Total Internal Reflection ◽  
Index Of Refraction ◽  
Optical Measurements ◽  
Lithium Ions ◽  
Wide Channel ◽  
Tem Characterization

An optical waveguide consists of a several-micron wide channel with a slightly different index of refraction than the host substrate; light can be trapped in the channel by total internal reflection.Optical waveguides can be formed from single-crystal LiNbO3 using the proton exhange technique. In this technique, polished specimens are masked with polycrystal1ine chromium in such a way as to leave 3-13 μm wide channels. These are held in benzoic acid at 249°C for 5 minutes allowing protons to exchange for lithium ions within the channels causing an increase in the refractive index of the channel and creating the waveguide. Unfortunately, optical measurements often reveal a loss in waveguiding ability up to several weeks after exchange.

Coherent electron nanodiffraction from clean silver nano particles in a UHV STEM

1993 ◽  
Vol 51 ◽  
pp. 1058-1059
Author(s):  
J. Liu ◽  
M. Pan ◽  
G. E. Spinnler
Keyword(s):  
Supported Catalysts ◽  
Imaging Techniques ◽  
Nano Particles ◽  
Metal Particles ◽  
Shape Structure ◽  
Dynamical Simulations ◽  
Small Metal Particles ◽  
Extract Information

Small metal particles have peculiar chemical and physical properties as compared to bulk materials. They are especially important in catalysis since metal particles are common constituents of supported catalysts. The structural characterization of small particles is of primary importance for the understanding of structure-catalytic activity relationships. The shape and size of metal particles larger than approximately 5 nm in diameter can be determined by several imaging techniques. It is difficult, however, to deduce the shape of smaller metal particles. Coherent electron nanodiffraction (CEND) patterns from nano particles contain information about the particle size, shape, structure and defects etc. As part of an on-going program of STEM characterization of supported catalysts we report some preliminary results of CEND study of Ag nano particles, deposited in situ in a UHV STEM instrument, and compare the experimental results with full dynamical simulations in order to extract information about the shape of Ag nano particles.

TEM characterization of WSix films

1994 ◽  
Vol 52 ◽  
pp. 848-849
Author(s):  
V. C. Kannan ◽  
S. M. Merchant ◽  
R. B. Irwin ◽  
A. K. Nanda ◽  
M. Sundahl ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Vapor Deposition ◽  
High Purity ◽  
Physical Vapor Deposition ◽  
Thermal Treatments ◽  
Rapid Thermal Anneal ◽  
Tungsten Silicide ◽  
Tem Characterization ◽  
Metal Silicides

Metal silicides such as WSi2, MoSi2, TiSi2, TaSi2 and CoSi2 have received wide attention in recent years for semiconductor applications in integrated circuits. In this study, we describe the microstructures of WSix films deposited on SiO2 (oxide) and polysilicon (poly) surfaces on Si wafers afterdeposition and rapid thermal anneal (RTA) at several temperatures. The stoichiometry of WSix films was confirmed by Rutherford Backscattering Spectroscopy (RBS). A correlation between the observed microstructure and measured sheet resistance of the films was also obtained.WSix films were deposited by physical vapor deposition (PVD) using magnetron sputteringin a Varian 3180. A high purity tungsten silicide target with a Si:W ratio of 2.85 was used. Films deposited on oxide or poly substrates gave rise to a Si:W ratio of 2.65 as observed by RBS. To simulatethe thermal treatments of subsequent processing procedures, wafers with tungsten silicide films were subjected to RTA (AG Associates Heatpulse 4108) in a N2 ambient for 60 seconds at temperatures ranging from 700° to 1000°C.

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