STRUCTURAL ANALYSIS OF Li2O·14Nb2O5 BY COMBINED CONVERGENT-BEAM ELECTRON DIFFRACTION AND HIGH RESOLUTION ELECTRON MICROSCOPY

ABSTRACTThe metamict transformation under electron irradiation has been studied in α-quartz using transmission electron microscopy (TEM) and convergent-beam electron diffraction (CBD). The transformation occurs in two stages: heterogeneous nucleation of discrete disordered inclusions and a slower homogeneous loss of crystalline order in the surrounding matrix. Both features are attributable to solidstate radiolysis, a mechanism for which is proposed. Ultrahigh resolution TEM structure images and information from zeroth and high order Laue zones in CBD confirm that shortrange correlations are the first to be lost and that longerrange correlations persist well into the metamict transformation. A transformation model is advanced in which progressive disorder evolves from small displacements of individual [SiO4] coordination units, made possible by lowered connectivity, within a framework of long-range ordered material.

Download Full-text

Microstructure of High Temperature Superconductors of the Perovskite Type

Australian Journal of Physics ◽

10.1071/ph870547 ◽

1987 ◽

Vol 40 (4) ◽

pp. 547 ◽

Cited By ~ 4

Author(s):

AF Moodie ◽

HJ Whitfield

Keyword(s):

Electron Microscopy ◽

High Temperature ◽

High Temperature Superconductor ◽

High Temperature Superconductors ◽

High Resolution Electron Microscopy ◽

Convergent Beam Electron Diffraction ◽

Beam Electron ◽

Resolution Electron ◽

Convergent Beam ◽

Perovskite Type

Combined high resolution electron microscopy and convergent beam electron diffraction (CBED) of the same areas of crystals of Ba3La3Cu6014 reveals defects of various types including ordinary dislocations and polytypic intergrowths. This latter type is considered to be intimately associated with the performance of this material as a high temperature superconductor ..

Download Full-text

The Structure of GaAs Grown by Chemical Beam Epitaxy on Low-Temperature Cleaned Silicon

MRS Proceedings ◽

10.1557/proc-281-333 ◽

1992 ◽

Vol 281 ◽

Author(s):

Y. R. Xing ◽

C. J. Kiely ◽

P. J. Goodhew

Keyword(s):

Electron Microscopy ◽

Low Temperature ◽

Defect Density ◽

High Resolution Electron Microscopy ◽

Convergent Beam Electron Diffraction ◽

Chemical Beam Epitaxy ◽

Beam Electron ◽

Resolution Electron ◽

Convergent Beam

ABSTRACTChemical beam epitaxy (CBE) has been used to grow GaAs on silicon with a low defect density after etching in HF followed by a low temperature (600°C) in situ heat treatment. High resolution electron microscopy (HREM) and convergent beam electron diffraction (CBED) studies show the presence of 90° and 60° dislocations and some inversion domains.

Download Full-text

Structural analysis of the surface-layer protein of spirillum serpens by high-resolution electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100077268 ◽

1983 ◽

Vol 41 ◽

pp. 738-739

Author(s):

W. H. Wu ◽

R. M. Glaeser

Keyword(s):

Electron Microscopy ◽

Surface Layer ◽

Structural Analysis ◽

High Resolution ◽

Low Dose ◽

High Resolution Electron Microscopy ◽

Optical Diffraction ◽

Surface Layer Protein ◽

Morphological Unit ◽

Resolution Electron

Spirillum serpens possesses a surface layer protein which exhibits a regular hexagonal packing of the morphological subunits. A morphological model of the structure of the protein has been proposed at a resolution of about 25 Å, in which the morphological unit might be described as having the appearance of a flared-out, hollow cylinder with six ÅspokesÅ at the flared end. In order to understand the detailed association of the macromolecules, it is necessary to do a high resolution structural analysis. Large, single layered arrays of the surface layer protein have been obtained for this purpose by means of extensive heating in high CaCl2, a procedure derived from that of Buckmire and Murray. Low dose, low temperature electron microscopy has been applied to the large arrays.As a first step, the samples were negatively stained with neutralized phosphotungstic acid, and the specimens were imaged at 40,000 magnification by use of a high resolution cold stage on a JE0L 100B. Low dose images were recorded with exposures of 7-9 electrons/Å2. The micrographs obtained (Fig. 1) were examined by use of optical diffraction (Fig. 2) to tell what areas were especially well ordered.

Download Full-text