Dislocations in YBa2Cu3O7−δ (δ = 0.77)

1990 ◽  
Vol 48 (4) ◽  
pp. 72-73
Author(s):  
Yimei Zhu ◽  
Hong Zhang ◽  
A.R. Moodenbaugh ◽  
M. Suenaga
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Displacement Vector ◽  
Stacking Faults ◽  
Spot Size ◽  
Convergent Beam Electron Diffraction ◽  
Burgers Vector ◽  
Beam Electron ◽  
X Ray ◽  
Convergent Beam

Abundant dislocations and dislocations associated with stacking faults were observed and characterized in YBa2Cu3O7−δ (δ= 0.77). The crystallographic orientation of the dislocation and the fault were analyzed using Kikuchi patterns matched with computer generated Kikuchi maps. The Burgers vector of the dislocation and the displacement vector of the fault were determined by using the g·b = 0 and g · R=0 criteria.Bulk samples of YBa2Cu3O7 were produced by standard pressing and sintering up to 970 °C. Samples were heated in air, then quenched into liquid nitrogen to reduce oxygen content. Subsequent anneal at 200 ° C took place with samples sealed in silica with 1/2 atm. of argon. TEM specimens were thinned by ion mill and examined in a JEOL 2000FX electron microscope operating at 200kv.X-ray powder diffraction and convergent beam electron diffraction with 200 Å spot size show that YBa2Cu3O6.23 has a tetragonal structure.

Lattice misfit by convergent-beam electron diffraction - Part I: Geometry measurement

1984 ◽  
Vol 42 ◽  
pp. 520-521
Author(s):  
L. S. Lin ◽  
J. M. Walsh
Keyword(s):  
Electron Diffraction ◽  
Conventional Method ◽  
Lattice Misfit ◽  
Spot Size ◽  
Convergent Beam Electron Diffraction ◽  
Beam Electron ◽  
X Ray ◽  
Peak Broadening ◽  
Geometry Measurement ◽  
Convergent Beam

The conventional method of lattice misfit determination in superalloys has involved the use of x-ray diffraction employing a parafocal camera. While the inherent accuracy and reliability of measurements made by such a technique is widely known, the value of any lattice parameters obtained represent an average for the volume characterized by the x-ray beam. Furthermore, the effects of enforced coherency between the γ and γ' phases in nickel-base superalloys often result in considerable peak broadening, so that the fundamental γ and γ̍ reflections are not resolved. Convergent beam electron diffraction (CBED) provides high spatial resolution for lattice misfit measurement (100 nm or smaller spot size) and overcomes some of the problems with the conventional method of measurement. The procedures used in the current CBED work are based on a geometrical analysis first described by Steeds. When a (111) zone axis beam direction is used a characteristic triangle formed by various ﹛359﹜ holz lines appears in the zero order central disc as shown in Figure 1 when operating at 100 kV.

scholarly journals Influence of Doping on the Crystal Potential of Silicon investigated by the Convergent Beam Electron Diffraction Technique

1980 ◽  
Vol 35 (9) ◽  
pp. 973-984 ◽  
Author(s):  
R. Voss ◽  
G. Lehmpfuhl ◽  
P. J. Smith
Keyword(s):  
Electron Diffraction ◽  
Excellent Agreement ◽  
Convergent Beam Electron Diffraction ◽  
Index Structure ◽  
Beam Electron ◽  
X Ray ◽  
Crystal Potential ◽  
Small Crystal ◽  
Electron Diffraction Technique ◽  
Convergent Beam

Abstract Low index structure potentials of silicon were determined by convergent beam electron diffraction (Kossel-Möllenstedt technique) from very small crystal areas of about 100 Å in diameter. The values of 111, 222, 220, 113 and 004, determined to an accuracy of ±0.03 volts, are in excellent agreement with the accurate X-ray results of Aldred and Hart (see [6], p. 239). Heavy arsenic or phosphorous doping was found to cause a shift of 0.15 volts in the 111 structure potential. Absorption potentials were also determined and found to be 1/3 of the theoretical values published by Radi [20].

Thickness dependence of the intensities of the 200 forbidden reflections in the TiBe2 diamond type structure

1988 ◽  
Vol 46 ◽  
pp. 826-827
Author(s):  
Dang-Rong Liu ◽  
D. B. Williams
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Convergent Beam Electron Diffraction ◽  
Type Structure ◽  
Beam Electron ◽  
Space Group ◽  
X Ray ◽  
Electron Diffraction Technique ◽  
Convergent Beam ◽  
Diamond Type

It is interesting to note that for the diamond type structure of Si, Ge and diamond, the forbidden {200} reflections in the exact <100> orientation diffraction pattern cannot be seen. In contrast, we also note a standing controversy over the structure of the MgAl2O4, spinel. Its structure was determined long ago by x-ray powder method as Fd3m (the diamond type). However, its electron diffraction pattern taken in the <100> orientation shows weak {200} reflections, which are taken as evidence that the spinel should have the space group F43m (the blende type), rather than Fd3m. Others speculate that these {200} reflections result from the high order Laue zone (HOLZ) reflections, and the spinel should be Fd3m. Nevertheless, still others think that these analyses are not conclusive. We have carefully studied the space group of TiBe2 using the convergent beam electron diffraction technique, and unambiguously demonstrated that its space group must be Fd3m.

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