X-Ray Measurement Methods From Chapter 6 of Textbook 2 and other references Diffractometer Hull/Debye-Scherrer method Pinhole method Laue Method Rotating Crystal Method http://www.stanford.edu/group/glam/ xlab/MatSci162_172/LectureNotes/ 06_Geometry,%20Detectors.pdf
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X-Ray Measurement Methods From Chapter 6 of Textbook 2 and other references Diffractometer Hull/Debye-Scherrer method Pinhole method Laue Method Rotating.
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X-Ray Measurement MethodsFrom Chapter 6 of Textbook 2 and other references
S: source; C: specimen; H: goniometer; O: rotation axis;A, B: slits for collimation; F: slit; G: detector;E and H can be mechanically; coupled 2 and relation;
Schematics of a typical X-ray diffractometer:
)2/cos( R
focusing monochromator
CM = 2R, OC = R Cut off the crystal behind the dotted line to a radius R
According to Euclid: “the angles in the same segment of a circle are equal to one another” and “the angle at the center of a circle is double that of the angle at the circumference on the same base, that is, on the same arc”.
Modern Bragg-Brentano laboratory diffractometer
Parallel beam geometry in Debye-Scherrer mode using a double monochromator (DM) and an analyzer crystal
Polycrystal
Single crystal
An ideal powder sample many crystallites in random orientations; smooth and constant distribution of orientations; Crystallites < 10 μm
Sample preparation: There are many methods of preparing samples: – Sample should normally be ground to < 10 μm – Sample may be sieved to avoid large or small crystallites – Sample may be loaded into a holder by pressing from the back while using a slightly rough surface at the front – Sample may be pressed in from the front – Sample may be mixed with a binder (epoxy or similar material) and then cut and polished to give a suitable surface