Microstructure of La1–xCaxMnO3 studied by transmission electron microscopy

2001 ◽  
Vol 16 (10) ◽  
pp. 2959-2965 ◽  
Author(s):  
Q. Chen ◽  
J. Tao ◽  
J. J. Zuo ◽  
J. J. H. Spence
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Colossal Magnetoresistance ◽  
Displacement Vector ◽  
Orthorhombic Unit Cell ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Synthesis Routes ◽  
Colossal Magnetoresistance Effect ◽  
The Ideal

Microstructures of La1-xCaxMnO3 compounds (x = ⅓ and 0.5) prepared with and without intermediate grinding were studied using transmission electron microscopy. A high density of antiphase boundaries (APBs) with displacement vector 1/2 〈111〉, indexed in orthorhombic unit cell, has been observed in bulk samples with no or minimum intermediate grinding. The nature of this APB is analyzed and found to bedue to the symmetry breaking introduced by the tilting of MnO6 octahedra relative to the ideal perovskite structure. Samples prepared using two intermediate grinds do not show these defects indicating that the microstructure can be controlled through synthesis routes. The effect of domain boundaries on the colossal magnetoresistance effect is discussed.

Oxygen incorporation in aluminum nitride via extended defects: Part II. Structure of curved inversion domain boundaries and defect formation

1995 ◽  
Vol 10 (5) ◽  
pp. 1287-1300 ◽  
Author(s):  
Alistair D. Westwood ◽  
Robert A. Youngman ◽  
Martha R. McCartney ◽  
Alastair N. Cormack ◽  
Michael R. Notis
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Aluminum Nitride ◽  
Displacement Vector ◽  
Interfacial Structure ◽  
Formation Mechanisms ◽  
Inversion Domain ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Inversion Domain Boundaries

Three distinct morphologies of curved (curved, facetted, and corrugated) inversion domain boundaries (IDB's), observed in aluminum nitride, have been investigated using conventional transmission electron microscopy, convergent beam electron diffraction, high-resolution transmission electron microscopy, analytical electron microscopy, and atomistic computer simulations. The interfacial structure and chemistry of the curved and facetted defects have been studied, and based upon the experimental evidence, a single model has been proposed for the curved IDB which is consistent with all three observed morphologies. The interface model comprises a continuous nitrogen sublattice, with the aluminum sublattice being displaced across a {1011} plane, and having a displacement vector R = 0.23〈0001〉. This displacement translates the aluminum sublattice from upwardly pointing to downwardly pointing tetrahedral sites, or vice versa, in the wurtzite structure. The measured value of the displacement vector is between 0.05〈0001〉 and 0.43〈0001〉; the variation is believed to be due to local changes in chemistry. This is supported by atomistic calculations which indicate that the interface is most stable when both aluminum vacancies and oxygen ions are present at the interface, and that the interface energy is independent of displacement vector in the range of 0.05〈0001〉 to 0.35〈0001〉. The curved IDB's form as a result of nonstoichiometry within the crystal. The choice of curved IDB morphology is believed to be controlled by local changes in chemistry, nonstoichiometry at the interface, and proximity to other planar IDB's (the last reason is explained in Part III). A number of possible formation mechanisms are discussed for both planar and curved IDB's. The Burgers vector for the dislocation present at the intersection of the planar and curved IDB's was determined to be b = 1/3〈1010〉 + t〈0001〉, where tmeas = 0.157 and tcalc = 0.164.

Nucleation of Disorder in Fe3Al Alloys

1967 ◽  
Vol 25 ◽  
pp. 312-313
Author(s):  
P. R. Swann ◽  
W. R. Duff ◽  
R. M. Fisher
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Annealing Temperature ◽  
Antiphase Domain ◽  
Effect Of Temperature ◽  
Domain Structures ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Higher Temperature ◽  
The One

Recently we have investigated the phase equilibria and antiphase domain structures of Fe-Al alloys containing from 18 to 50 at.% Al by transmission electron microscopy and Mössbauer techniques. This study has revealed that none of the published phase diagrams are correct, although the one proposed by Rimlinger agrees most closely with our results to be published separately. In this paper observations by transmission electron microscopy relating to the nucleation of disorder in Fe-24% Al will be described. Figure 1 shows the structure after heating this alloy to 776.6°C and quenching. The white areas are B2 micro-domains corresponding to regions of disorder which form at the annealing temperature and re-order during the quench. By examining specimens heated in a temperature gradient of 2°C/cm it is possible to determine the effect of temperature on the disordering reaction very precisely. It was found that disorder begins at existing antiphase domain boundaries but that at a slightly higher temperature (1°C) it also occurs by homogeneous nucleation within the domains. A small (∼ .01°C) further increase in temperature caused these micro-domains to completely fill the specimen.

Multiple twinning of diamond synthesized by acetylene flame

2004 ◽  
Vol 219 (8) ◽  
Author(s):  
Sam Ick Son ◽  
Su Jin Chung
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Electron Back Scatter Diffraction ◽  
The Other ◽  
Hrtem Image ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Multiple Twinning ◽  
Ebsd Method

AbstractThe relation between the domains and domain boundaries of multiple twins of diamond were investigated by the electron back scatter diffraction (EBSD) method and high resolution transmission electron microscopy (HRTEM). Multiple twinned diamonds have two types of icosahedral morphologies. One is an almost perfect icosahedron in which all of the faces are {111} faces. The other is a hollow icosahedron similar to one of the Kepler-Poinsot polyhedrons. The indented negative trigonal faces are formed from the {100} faces of a cube. It was confirmed that the convex edges of the twinned icosahedron corresponded to the Σ3 boundaries, whereas the concave edges were assigned to the Σ9 twin boundary by means of the EBSD analysis.It was confirmed from the HRTEM image that a series of dislocations compensate for the mismatching angle which occurs after five successive twinning.

Observation of antiphase domain boundaries in GaAs on silicon by transmission electron microscopy

1988 ◽  
Vol 53 (13) ◽  
pp. 1207-1209 ◽  
Author(s):  
J. B. Posthill ◽  
J. C. L. Tarn ◽  
K. Das ◽  
T. P. Humphreys ◽  
N. R. Parikh
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Antiphase Domain ◽  
Transmission Electron ◽  
Domain Boundaries

Stacking Faults on (001) in Transition-Metal Disilicides with The Cllb Structure

1996 ◽  
Vol 460 ◽  
Author(s):  
K. Ito ◽  
T. Nakamoto ◽  
H. Inui ◽  
M. Yamaguchi
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Displacement Vector ◽  
Stacking Faults ◽  
Repulsive Interaction ◽  
Floating Zone ◽  
Zone Method ◽  
Floating Zone Method ◽  
Transmission Electron ◽  
High Resolution Tem

ABSTRACTStacking faults on (001) in MoSi2 and WSi2 with the Cllb structure have been characterized by transmission electron microscopy (TEM), using their single crystals grown by the floating-zone method. Although WSi2 contains a high density of stacking faults, only several faults are observed in MoSi2. For both crystals, (001) faults are characterized to be of the Frank-type in which two successive (001) Si layers are removed from the lattice, giving rise to a displacement vector parallel to [001]. When the displacement vector of faults is expressed in the form of R=l/n[001], however, their n values are slightly deviated from the exact value of 3, because of dilatation of the lattice in the direction perpendicular to the fault, which is caused by the repulsive interaction between Mo (W) layers above and below the fault. Matching of experimental high-resolution TEM images with calculated ones indicates n values to be 3.12 ± 0.10 and 3.34 ± 0.10 for MoSi2 and WSi2, respectively.

scholarly journals Effect of screw threading dislocations and inverse domain boundaries in GaN on the shape of reciprocal-space maps

2017 ◽  
Vol 50 (2) ◽  
pp. 555-560 ◽  
Author(s):  
Mykhailo Barchuk ◽  
Mykhaylo Motylenko ◽  
Gleb Lukin ◽  
Olf Pätzold ◽  
David Rafaja
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Reciprocal Space ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
Reciprocal Space Mapping ◽  
Vapour Phase Epitaxy ◽  
X Ray ◽  
Transmission Electron ◽  
Domain Boundaries

The microstructure of polar GaN layers, grown by upgraded high-temperature vapour phase epitaxy on [001]-oriented sapphire substrates, was studied by means of high-resolution X-ray diffraction and transmission electron microscopy. Systematic differences between reciprocal-space maps measured by X-ray diffraction and those which were simulated for different densities of threading dislocations revealed that threading dislocations are not the only microstructure defect in these GaN layers. Conventional dark-field transmission electron microscopy and convergent-beam electron diffraction detected vertical inversion domains as an additional microstructure feature. On a series of polar GaN layers with different proportions of threading dislocations and inversion domain boundaries, this contribution illustrates the capability and limitations of coplanar reciprocal-space mapping by X-ray diffraction to distinguish between these microstructure features.

Features of the ferroelectric domain structure in the multiferroic material YbMnO3

MRS Advances ◽  
2016 ◽  
Vol 1 (9) ◽  
pp. 591-596
Author(s):  
Takumi Inoshita ◽  
Yasuhide Inoue ◽  
Yoichi Horibe ◽  
Yasumasa Koyama
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Domain Structure ◽  
Ferroelectric Domain ◽  
Multiferroic Material ◽  
Ferroelectric State ◽  
Hexagonal Axis ◽  
Domain Structures ◽  
Transmission Electron ◽  
Domain Boundaries

ABSTRACTThe multiferroic material YbMnO3 has been reported to exhibit both ferroelectric and antiferromagnetic orders in the ground state. Of these two orders, the ferroelectric order is associated with the P63/mmc-to-P63cm structural transition, which occurs around 1270 K. The interesting feature of the ferroelectric state is that a cloverleaf domain structure with a pseudo-six-fold symmetry is observed in transmission electron microscopy images with the beam incidence parallel to the hexagonal axis. To understand the origin of the formation of the cloverleaf domain structure, we have examined the crystallographic features of the ferroelectric state in YbMnO3 by transmission electron microscopy. In this study, particularly, we adopted the experimental condition that electron beam incidences are perpendicular to the hexagonal axis. It was, as a result, found that there existed various ferroelectric domain structures including the cloverleaf domain structure under the present condition. The notable feature of domain structures found in this study is that each domain structure basically consists of six domains, whose domain boundaries are terminated at one point. Because this feature makes us reminiscent of a discommensurate structure in an incommensurate state, we took high-resolution electron micrographs of areas including domain boundaries. Their analysis indicated that a domain boundary could be identified as a discommensuration with a phase slip of π/3. It is thus understood that the cloverleaf domain structure should be one of domain morphologies for a discommensurate structure, which is related to the break of the translational symmetry.

scholarly journals Investigations on domain boundaries in ordered GaInP using stereo transmission electron microscopy

1997 ◽  
Vol 22 (3) ◽  
pp. 301-305 ◽  
Author(s):  
G. Hahn ◽  
C. Geng ◽  
P. Ernst ◽  
H. Schweizer ◽  
F. Scholz ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Transmission Electron ◽  
Domain Boundaries
Sign in / Sign up

Export Citation Format

Share Document