Debye-Scherrer type pattern

Figure 4 corresponds to PETPg (Ag2S stained) with 12 different selected areas and corresponding diffraction patterns. One can see that 5 patterns have the same orientation, 3 are practically at right angles from the latter, 2 have an intermediate orientation and the last 2 are highly disoriented, with one Debye Scherrer type pattern. 

Local Orientation. The most striking observation of this work is that the selected area diffraction patterns are not in general of a Debye-Scherrer type. Among the various hypotheses which can be drawn to understand such a fact, the most probable one is that the sections are not truly transverse ones indeed, if one supposes the existence of a cylindrical symmetry at the level of each selected area, 0.5 to 1 ym in diameter (the symmetry axis being always parallel to the fiber axis) the "detectable" network main planes have to be parallel to 1he "c" axis of the individual... 

There are two different ways to get local diffraction patterns "Debye-Scherrer" type (such patterns are obtained if ( y ) is found within (E). In the first case (figure 15 the orientation of the local symmetry axis ( A ) is very close to that of (I) with the consequence tRat the whole cone ( e ) is located within the cone (C) even if the local orientation is relatively good, i.e., angle 0 is small. In the second case, the local orientation is poorer, i.e., 0 is fairly large. 

Various kinds of special cameras have been devised for obtaining diffraction patterns from specimens subjected to unusual conditions of temperature or pressure [G.39]. These cameras, usually of the Debye-Scherrer type and usually homemade, have designs that vary almost from laboratory to laboratory. 

The lattice factor can be considered to sample the structure factor at different points in reciprocal space and the observed diffraction pattern is essentially a two-dimensional projection of the square of this sampling. For samples which are polycrystalline in nature (Le, the grains are randomly oriented) the diffraction patterns are of the Debye-Scherrer type consisting of concentric rings. When the structural units are oriented along a particular axis the rings give way to broad spots, the distribution of which can reveal the orientation of the specimen. ... 

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