Electron microscopy of the commensurate-incommensurate phase transition with the discommensuration network in 1T-TaS2

1990 ◽  
Vol 48 (4) ◽  
pp. 168-169
Author(s):  
Takashi Ishiguro ◽  
Hiroshi Sato
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Transmission Electron Microscopy ◽  
Phase Transitions ◽  
High Resolution ◽  
Low Temperature ◽  
Transmission Electron ◽  
Continuous Rotation ◽  
T Phase ◽  
New Phase

Phase transitions of lT-TaS2 both on cooling from the incommensurate (IC) phase and on heating from the commensurate (C) phase are investigated by high resolution (HR) transmission electron microscopy because phase transitions are strongly hysteretic. The phases which had been identified were Normal(T>543K,no modurated wave, the Cdl2 type of structure, ao=0.336nm co=0.590nm), IC(354K< T< 543K), NC(non-commensurate or nearly commensurate, 185K<T<353K) and C(T<K). On heating from the C phase, the new phase called the T phase (nearly commensurate triclinic ) appears between 200K and 280K, and that has the discommensuration (DC) network. The HR observations at low temperature reveal both the three dimentional structure of the C phase and the DC network structure of the T phase.On cooling from the IC phase, the structure of the NC phase is essentially incommensurate in the basal plane and a continuous rotation of the moduration direction towards the C phase occurs.

6H-Type Zigzag Faults in Low-Doped 4H-SiC Epitaxial Layers

2010 ◽  
Vol 645-648 ◽  
pp. 347-350 ◽  
Author(s):  
Teddy Robert ◽  
Maya Marinova ◽  
Sandrine Juillaguet ◽  
Anne Henry ◽  
Efstathios K. Polychroniadis ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Low Temperature ◽  
Liquid Helium ◽  
Helium Temperature ◽  
Transmission Electron ◽  
Unit Cells ◽  
New Type ◽  
Low Temperature Photoluminescence

A new type of 6H zigzag faults has been identified from high resolution transmission electron microscopy (HRTEM) measurements performed on low-doped 4H-SiC homoepitaxial layer grown on off-axis substrates in a hot-wall CVD reactor. They are made of half unit cells of 6H with corresponding low temperature photoluminescence (LTPL) response ranging from about 3 eV to 2.5 eV at liquid helium temperature.

Study of Precipitation Sequence in Al-Mg-Si Alloys by HRTEM

2005 ◽  
Vol 475-479 ◽  
pp. 361-364 ◽  
Author(s):  
Kenji Matsuda ◽  
Susumu Ikeno
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Low Temperature ◽  
Early Stage ◽  
Metastable Phases ◽  
Precipitation Sequence ◽  
Mono Layer ◽  
Transmission Electron

The precipitation sequence of Al-Mg-Si alloys has been studied by high-resolution transmission electron microscopy (HRTEM). G.P. zone is a fine-plate having dimensions of a mono- layer in thickness, 2.5nm in width, and less than 30nm in length. Its elongated direction is parallel to the <100>m direction. Several types of metastable phases were observed in the excess Si alloy and they were classified with the b ’-phase in the balanced alloy. Especially, the b ”-phase was the typical phase in the excess Si alloy aged at low temperature or at the early stage during aging.

HRTEM analysis on phase transitions in Bi-based superconductive oxides

1990 ◽  
Vol 48 (4) ◽  
pp. 22-23
Author(s):  
S. Horiuchi ◽  
K. Shoda ◽  
X.J. Wu ◽  
H. Nozaki ◽  
M. Tsutsumi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Transmission Electron Microscopy ◽  
Phase Transitions ◽  
Structural Variation ◽  
Molten State ◽  
Critical Temperatures ◽  
Transmission Electron ◽  
Higher Temperature ◽  
Ice Water

It is known for the superconductors in a Bi-Sr-Ca-Cu-O system that there are three phases. Bi2Sr2CuOx, Bi2Sr2CaCu2Ox and Bi2Sr2Ca2Cu3Ox, which are called for simplicity the (2201), (2212) and (2223) phases with the critical temperatures Tc at about 20, 85 and 110K respectively. Their crystal structures are closely related and the phase transition among them often occurs. When the specimen in the partially molten state was quenched to ice-water, it was composed of a Bi-rich, amorphous phase and impurity phases like Ca1−zSrzCuO2. On crystallization the former became the (2201) phase. On further heating at higher temperature firstly the (2212) phase and secondly the (2223) phase were obtained.In the present study the structural variation during the transition from the (2201) phase to the (2212) phase and further to the (2223) phase was clarified mainly by using a high-resolution transmission electron microscopy (IIRTEM). Thin specimens were prepared by ion-thinning method and observed by a 200kV TEM (JEM 2000EX). The mechanism of the phase transition was discussed from the structural viewpoint.

HREM study of ferroelectric domain wall in barium titanate

1994 ◽  
Vol 52 ◽  
pp. 566-567
Author(s):  
Laurent. Normand ◽  
Alain. Thorel ◽  
Yvan. Montardi
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Barium Titanate ◽  
Domain Walls ◽  
Ferroelectric Phase ◽  
Ferroelectric Domain ◽  
Transmission Electron ◽  
The One

This study focuses on High Resolution Transmission Electron Microscopy of barium titanate in its tetragonal ferroelectric phase, and especially on the structure of domain walls. This phase is stable between about 0 °C and 130 °C. During cooling, at 130 °C barium titanate changes from a cubic parraelectric phase to a tetragonal ferroelectric phase. In this phase the spontaneous polarisation is along one of the six [001] pseudo-cubic directions. Two types of domains can be formed during the phase transition :90° and 180° domains. In 90° domains the polarisation is at 90° from the polarisation of the next domain (exactly 2* ArcTan(a/c) if a and c are the lattice parameters). For these domains the domain walls are <110< type planes ; In 180° domains the polarisation is at 180° from the one in the next domain. 180° domain walls are <100< type plane and are assumed to be purely ferroelectric.

scholarly journals Особенности структуры германия, обработанного в планетарной мельнице

2020 ◽  
Vol 62 (10) ◽  
pp. 1597
Author(s):  
Т.А. Гордеева ◽  
Д.А. Овсянников ◽  
М.Ю. Попов ◽  
Б.А. Кульницкий ◽  
В.Д. Бланк
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Diamond Powder ◽  
Planetary Mill ◽  
Transmission Electron ◽  
Germanium Powder

In this work high-resolution transmission electron microscopy (HRTEM) studies of germanium powder obtained as a result of processing in a planetary mill in the presence of (5-25%) of diamond powder have been performed. As a result of processing sample contains twins on {111} plane and packaging defects in germanium. Phase 9R was detected in which the following sequence of layers takes place: ...BABCBCACA... In some particles, there was a partial or complete phase transition of GeI → GeIV and GeI → GeIII.

A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

1982 ◽  
Vol 40 ◽  
pp. 722-723 ◽  
Author(s):  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Computer Simulations ◽  
Structural Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

Microstructure of laser-irradiated, conducting Kapton polyimide

1995 ◽  
Vol 53 ◽  
pp. 502-503
Author(s):  
D. L. Callahan ◽  
Z. Ball ◽  
H. M. Phillips ◽  
R. Sauerbrey
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Transmission Electron Microscopy ◽  
Cross Section ◽  
Film Surface ◽  
Cross Sectional ◽  
General Utility ◽  
Transmission Electron ◽  
Considerable Debate ◽  
Potential Applications

Ultraviolet laser-irradiation can be used to induce an insulator-to-conductor phase transition on the surface of Kapton polyimide. Such structures have potential applications as resistors or conductors for VLSI applications as well as general utility electrodes. Although the percolative nature of the phase transformation has been well-established, there has been little definitive work on the mechanism or extent of transformation. In particular, there has been considerable debate about whether or not the transition is primarily photothermal in nature, as we propose, or photochemical. In this study, cross-sectional optical microscopy and transmission electron microscopy are utilized to characterize the nature of microstructural changes associated with the laser-induced pyrolysis of polyimide.Laser-modified polyimide samples initially 12 μm thick were prepared in cross-section by standard ultramicrotomy. Resulting contraction in parallel to the film surface has led to distortions in apparent magnification. The scale bars shown are calibrated for the direction normal to the film surface only.

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