Infinitesimal loops and tweed structure

1995 ◽  
Vol 45 (11) ◽  
pp. 893-906 ◽  
Author(s):  
L. M. Brown
Keyword(s):  
Tweed Structure

TEM studies of tweed microstructures in annealed amelia albite

1990 ◽  
Vol 48 (4) ◽  
pp. 1064-1065
Author(s):  
Y. J. Kim ◽  
D. M. Henderson
Keyword(s):  
Annealing Time ◽  
The Other ◽  
Frequency Of Occurrence ◽  
Systematic Trend ◽  
Tweed Structure

Natural Amelia albite (Ab99.3An0.1Or0.6) annealed at 1073° and 924°C for various periods up to 140 days has been studied by NMR. TEM studies of the same sample revealed a distinct tweed microstructure in some samples annealed at both 1073°C and 924°C. On the whole, the quasi-regular tweed has a periodicity of 100 - 200 Å in both directions, one nearly normal to b* and the other approximately parallel to b*, which gives rise to two-directional streaking in SADP’s (Fig. 1 and 2). However, there are some differences in the tweed structure developed on annealing at 1073°C and at 924°C in albite.Albite samples annealed at 1073° show a systematic trend in their development of tweed structures: the regularity, periodicity, and frequency of occurrence increase with annealing time during the first 3 days, and then decrease gradually until no tweed microstructures are seen in samples annealed for more than 15 days. The tweed structure proceeds locally to form one-directional twin-like microstructures.

Phase transformation of metastable beta Ti alloys with tweed structure

2005 ◽  
Vol 11 (5) ◽  
pp. 365-369 ◽  
Author(s):  
Byung-Hak Choe ◽  
Soo-Keun Shin ◽  
Yeong Ouk Kim ◽  
Yong-Teak Hyun ◽  
Seung-Eon Kim ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Ti Alloys ◽  
Tweed Structure ◽  
Metastable Beta

Tweed structure in YBa2Cu3O7–δ induced by reduction of the oxygen content

1992 ◽  
Vol 131 (1) ◽  
pp. K7-K12 ◽  
Author(s):  
G. Lacayo ◽  
G. Kästner
Keyword(s):  
Oxygen Content ◽  
Tweed Structure

Oxygen ordering and tweed structure inYBa2Cu3O6+xstudied by diffuse neutron scattering

1993 ◽  
Vol 48 (9) ◽  
pp. 6513-6518 ◽  
Author(s):  
W. Schwarz ◽  
O. Blaschko ◽  
G. Collin ◽  
F. Marucco
Keyword(s):  
Neutron Scattering ◽  
Oxygen Ordering ◽  
Tweed Structure ◽  
Diffuse Neutron

Tetragonal microdomains in partially reduced zirconia

1988 ◽  
Vol 46 ◽  
pp. 574-575
Author(s):  
Y. M. Kim
Keyword(s):  
Spinodal Decomposition ◽  
Strain Field ◽  
Isothermal Annealing ◽  
Antiphase Boundaries ◽  
Thick Disc ◽  
Moderate Rate ◽  
The Matrix ◽  
Tweed Structure ◽  
Cold Pressed

Tweed structure often forms when ZrO2-Y2O3 alloy is cooled at a moderate rate through the cubic plus tetragonal two-pnase field. Hannink1 and Ishizawa et al. have explained that tweed character comes from the strain field around fine tetragonal precipitates in a cubic matrix. Sakuma et al. have reported similar structures after isothermal annealing at appropriate temperature and composition and explained in terms of spinodal decomposition. But, Lanteri et al. have suggested that the matrix have transformed displacively to t-symmetry once sample is cooled rapidly, observing antiphase boundaries(APB's) in DF with [112] type reflections. There is still uncertainty on the microstructure of tweed structures. This study presents the microstructures obtained from vacuum sintered ZrO2-5mol Y2O3, that show fine tetragonal microdomains with APB's in a cubic matrix.A 10mm dia. by 2mm thick pellet was cold-pressed from a ZrO2-5mol % Y2O3 powder, sintered at 2000°C for 2 h in vacuum, and fast-cooled (from 2000°C to 1100°C in 4 min.). Then, a 0.7mm thick disc was cut, sintered again at 2000°C for 4 h and fast cooled. The specimens were reduced and were black in color.

Twinning and oxygen ordering in Ba2YCu3O7−x crystals

1990 ◽  
Vol 48 (4) ◽  
pp. 14-15
Author(s):  
Sumio Iijima ◽  
Toshinari Ichihashi
Keyword(s):  
Electron Beam ◽  
Electron Beam Irradiation ◽  
Structural Changes ◽  
Oxygen Deficiency ◽  
Phase 1 ◽  
Structural Evolution ◽  
Beam Irradiation ◽  
Oxygen Ordering ◽  
Tweed Structure ◽  
T Phase

Formation of twins in Or-BYCO crystals was studied by transforming them to T-phase by electron beam irradiation in the microscope. It is known that during the transformation the crystals developed twinning (STW), Ortho-II phase (1×2 superstructure), tweed structure. These structures occur in that order by the irradiation and the structural changes are caused by oxygen deficiency and oxygen atoms ordering. This work is aimed at elucidation of oxygen atom ordering by examining the structural evolution in terms of morphologies of the twins.Atypical evolution of an Or-BYCO crystal is shown in a series of micrographs in Figs. 1 to 5. As-grown twin (FTW) boundaries have a characteristic lens shape extending in the < 110> direction and terminate at a twin boundary in horizontal direction (Fig.1). These boundaries don't accompany strain contrast which is developed in the crystal after a brief irradiation (Fig.2). The strain contrasts, which are differentiated easily from the thickness contrast, appear parallel to the boundaries and change slowly across the boundaries.

Oxygen, diffuse scattering, and tweed structure in the YBa2Cu3O7-δ system

1991 ◽  
Vol 37 (1-4) ◽  
pp. 341-350 ◽  
Author(s):  
Yimei Zhu ◽  
M. Suenaga ◽  
A.R. Moodenbaugh
Keyword(s):  
Diffuse Scattering ◽  
Tweed Structure

Ferroelastic Nanostructures and Nanoscale Transitions: Ferroics with Point Defects

MRS Bulletin ◽  
2009 ◽  
Vol 34 (11) ◽  
pp. 838-846 ◽  
Author(s):  
Xiaobing Ren ◽  
Yu Wang ◽  
Kazuhiro Otsuka ◽  
Pol Lloveras ◽  
Teresa Castán ◽  
...  
Keyword(s):  
Glass Transition ◽  
Martensitic Transformation ◽  
Point Defects ◽  
Functional Materials ◽  
Modeling Simulation ◽  
Concise Review ◽  
Transition Strain ◽  
Tweed Structure ◽  
Strain Glass Transition ◽  
Ferroelastic Domains

AbstractFor decades, a kind of nanoscale microstructure, known as the premartensitic “tweed structure” or “mottled structure,” has been widely observed in various martensitic or ferroelastic materials prior to their martensitic transformation, but its origin has remained obscure. Recently, a similar nanoscale microstructure also has been reported in highly doped ferroelastic systems, but it does not change into martensite; instead, it undergoes a nanoscale freezing transition—“strain glass” transition—and is frozen into a nanodomained strain glass state. This article provides a concise review of the recent experimental and modeling/simulation effort that is leading to a unified understanding of both premartensitic tweed and strain glass. The discussion shows that the premartensitic tweed or strain glass is characterized by nano-sized quasistatic ferroelastic domains caused by the existence of random point defects or dopants in ferroelastic systems. The mechanisms behind the point-defect-induced nanostructures and glass phenomena will be reviewed, and their significance in ferroic functional materials will be discussed.

Simulation and interpretation of image contrast and diffuse scattering of tweed structure

1992 ◽  
Vol 50 (1) ◽  
pp. 90-91
Author(s):  
Yimei Zhu ◽  
Z.X. Cai ◽  
M. Suenaga ◽  
D.O. Welch
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Electron Diffraction Pattern ◽  
Order Parameter ◽  
Diffuse Scattering ◽  
Binary Alloys ◽  
Image Contrast ◽  
Statistical Fluctuation ◽  
Tweed Structure ◽  
Shed Light

The so-called tweed structure exhibits a roughly periodic lenticular-domain image (Fig.l) associated with the streaking of diffuse scattering around the fundamental reflections in an electron diffraction pattern (Fig.2(c)). Tweed was observed in high Tc oxides YBa2(Cu1-xMx)3O7-δ (M = Fe, Co, Al, x≥0.03; M = Cu, δ∼0.6-0.8), as well as in some binary alloys, which usually show statistical fluctuation in their composition or in an order parameter.Although tweed has long been studied, crystallographic aspects of tweed modulation is not well understood. To shed light on the details of the structure, we performed simulations both on the tweed image and diffuse scattering, based on our TEM observations of YBa2(Cu1-xMx)3O7-δ

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