Synthesis of BaAl2Si2O8 from solid Ba–Al–Al2O3–SiO2 precursors: Part III. The structure of BaAl2Si2O8 formed by annealing at ≤650 °C and at 1650 °C

1998 ◽  
Vol 13 (11) ◽  
pp. 3122-3134 ◽  
Author(s):  
Xiao-Dong Zhang ◽  
Kenneth H. Sandhage ◽  
Hamish L. Fraser
Keyword(s):  
Heat Treatment ◽  
Stacking Faults ◽  
Antiphase Boundaries ◽  
Analytical Tem ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

Analytical TEM and HREM have been used to examine the structure of BaAl2Si2O8 crystals produced within oxidized Ba–Al–Al2O3–SiO2 precursors upon annealing: (i) at ≤650 °C and (ii) up to 1650 °C. A BaAl2Si2O8 polymorph with a c-axis parameter of 15.6 Å was detected after annealing at ≤650 °C. Stacking faults and antiphase boundaries were detected within this polymorph after the 650 °C treatment. After a 15 h heat treatment at 1650 °C, convergent beam diffraction patterns and HREM confirmed that the predominant phase was β–hexacelsian. Although antiphase boundaries were absent in the β–hexacelsian crystals, dislocations and stacking faults were detected after the 1650 °C anneal. The generation of defects in BaAl2Si2O8 crystals within specimens annealed at ≤650 °C and at 1650 °C is discussed in light of prior structural analyses.

On the role of the second-order derivative term in the calculation of convergent beam diffraction patterns

2017 ◽  
Vol 179 ◽  
pp. 73-80 ◽  
Author(s):  
S.C. Hillier ◽  
E.T. Robertson ◽  
G.D. Reid ◽  
R.D. Haynes ◽  
M.D. Robertson
Keyword(s):  
Second Order ◽  
Order Derivative ◽  
Derivative Term ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

scholarly journals Particle size and convergent electron diffraction patterns of triangular prismatic gold nanoparticles

2021 ◽  
Vol 67 (4 Jul-Aug) ◽  
Author(s):  
Clemente Fernando-Marquez ◽  
Gilberto Mondragón-Galicia ◽  
Lourdes Bazán-Díaz ◽  
José Reyes-Gasga
Keyword(s):  
Particle Size ◽  
Gold Nanoparticles ◽  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Stacking Faults ◽  
Au Nanoparticle ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Fcc Structure

Convergent beam diffraction (CBED) patterns of nanoparticles are possible. CBED of triangular prismatic shaped Au nanoparticle with focus on diffraction pattern symmetry and forbidden reflections observed along [111] and [112] zone axes are reported in this work. It is well known that the CBED patterns of nanoparticles of 30 nm or less in size only show bright kinematical discs. The dynamic contrast with Kikuchi and sharp HOLZ lines within the bright discs, as observed in CBED of volumetric materials, is well observed in particles larger of 500 nm in size. In addition, it is shown that the 1/3[422] and 1/2[311] weak forbidden reflections observed in the [111] and [112] electron diffraction patterns of these particles do not modify the symmetry of the CBED patterns, but they disappear as the size of the particle increases. The symmetry of the CBED patterns are always observed in concordance with the space group Fm3m (No. 225) of the Au unit cell. The possible explanations for observing forbidden reflections are the incomplete ABC stacking due to surface termination and the stacking faults in the fcc structure.

One of my Failures: Diffraction in the TEM

2011 ◽  
Vol 19 (1) ◽  
pp. 72-72 ◽  
Author(s):  
Alwyn Eades
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Standard Method ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

There are two principal techniques for obtaining diffraction patterns in the transmission electron microscope (TEM). They are selected-area diffraction (SAD) and convergent-beam diffraction (CBED). CBED is quicker and easier to use, and it provides a much richer characterization of the sample. Thus, it is clear that CBED should be used in the vast majority of cases. It should be the diffraction technique that students learn first, and students should be taught to consider it the standard method of doing diffraction in the TEM.

Using the TEM Condenser Lens to Switch between Image and Diffraction Modes

2013 ◽  
Vol 21 (2) ◽  
pp. 40-40
Author(s):  
Lydia Rivaud
Keyword(s):  
Electron Microscope ◽  
Diffraction Pattern ◽  
Transmission Electron Microscope ◽  
Condenser Lens ◽  
Selected Area Diffraction Pattern ◽  
Transmission Electron ◽  
Set Up ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

Central to the operation of the transmission electron microscope (TEM) (when used with crystalline samples) is the ability to go back and forth between an image and a diffraction pattern. Although it is quite simple to go from the image to a convergent-beam diffraction pattern or from an image to a selected-area diffraction pattern (and back), I have found it useful to be able to go between image and diffraction pattern even more quickly. In the method described, once the microscope is set up, it is possible to go from image to diffraction pattern and back by turning just one knob. This makes many operations on the microscope much more convenient. It should be made clear that, in this method, neither the image nor the diffraction pattern is “ideal” (details below), but both are good enough for many necessary procedures.

Energy-filtered convergent-beam diffraction: examples and future prospects

1995 ◽  
Vol 59 (1-4) ◽  
pp. 1-13 ◽  
Author(s):  
P.A. Midgley ◽  
M. Saunders ◽  
R. Vincent ◽  
J.W. Steeds
Keyword(s):  
Future Prospects ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction
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