Powder Photographs 6-2 Debye-Scherrer method

The Raman samples themselves were used to obtain powder photographs by the Debye-Scherrer method. 

Figure 6.4 The Debye-Scherrer method for taking powder photographs. The angle RSX is 20, where 0 is the angle of incidence on a set of crystal planes (17).

FIGURE 27.2 Debye-Scherrer powder method. Cones of reflected and transmitted radiation are produced. In this example the pattern is recorded with photographic film. Alternatively,... 

The compound layer formed in the transition zone between nickel and bismuth was investigated metallographically, by X-rays and electron probe microanalysis (EPMA). X-ray patterns were taken both from the cross-sections in the planes parallel to the initial Ni-Bi interface (after successive removal of the specimen material and polishing its surface) and the powdered phases using Cu Ka radiation. Two methods of obtaining X-ray patterns were employed. Firstly, X-ray photographs were obtained in a 57.3 mm inner diameter Debye-Scherrer camera. Secondly, use was made of a DRON-3 diffractometer to record X-ray diffractograms. 

G.17 Leonid V. Azaroff and Martin J. Buerger. The Powder Method in X-Ray Crystallography (New York McGraw-Hill, 1958). The making and interpretation of Debye-Scherrer photographs, including precise parameter measurements. 

A Debye-Scherrer camera consists of a metal cylinder provided with a photographic film. The primary beam is perpendicular to its axis. The distance between two symmetrical lines, produced by the intersection of a cone with the cylinder, is 46R, 6 being the Bragg angle (in radians) and R the radius of the camera. The interval is derived from Bragg s law. The powder method gives us only the norms of the reciprocal vectors. The set of norms corresponds to the projection of the reciprocal lattice onto a straight line. 

The classical photographic method for recording powder diffraction patterns is still used, particularly when the amount of sample is small. The most common instrument forthis purpose is the Debye-Scherrer pov/det camera, which is shown schematically in Figure 12-17a. Here, the beam from an X-ray tube is filtered to produce a nearly monochromatic beam (often the copper or molybdenum Ka line), which is collimated by passage through a narrow tube. 

However, not every crystalline substance can be obtained in the form of macroscopic crystals. This led to the Debye-Scherrer (16) method of analysis for powdered crystalline solids or polycrystalline specimens. The crystals are oriented at random so the spots become cones of diffracted beams that can be recorded either as circles on a flat photographic plate or as arcs on a strip of film encircling the specimen (see Figure 6.4) (17). The latter method permits the study of back reflections as well as forward reflections. 

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