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Published byAllyson Leslie Chambers Modified over 9 years ago
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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 Crystal Method http://www.stanford.edu/group/glam/xlab/MatSci162_ 172/LectureNotes/06_Geometry,%20Detectors.pdf
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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:
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focusing monochromator CM = 2R, OC = R Cut off the crystal behind the dotted line to a radius R
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http://cheiron2008.spring8.or.jp/lec_text/Sep.30/2008_T.Matsushita_1.pdf
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X-ray Optics: Bragg-Brentano diffractometers 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”.
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Modern Bragg-Brentano laboratory diffractometer
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Parallel beam geometry in Debye-Scherrer mode using a double monochromator (DM) and an analyzer crystal
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Polycrystal Single crystal
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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
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Hull/Debye-Scherrer method: R S S 22 22 2 =S/R Film
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hole Film hole 22 22 22 22 S S 2S S S 22 R
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Film hole 22 22 22 S 22 R and Resolving power
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http://www.stanford.edu/group/glam/xlab/MatSci162_172 /LectureNotes/06_Geometry,%20Detectors.pdf
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B S r1r1 F 22 A B r2r2 F 180 o -2 D D tan2 = r 1 /Dtan(180 o -2 = r 2 /D C C A Incident X-Ray Pinhole photographs monochromatic or white radiation and powder sample Laue methode: white radiation and single crystal
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http://202.141.40.218/wiki/index.php/Unit- 2:_Introduction_to_X-ray_diffraction Rotating Crystal Method
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Concept of Ewald Sphere and Diffraction
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Wavelength: incident beam = diffracted beam Magnitude of k the same = 1/. Diffraction condition: k = G 2B2B 2 B k = G
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Diffraction Methods: Method Laue Variable fixed Rotating crystal Fixed Variable Powder Fixed Variable vaied reciprocal lattice is rotated or Ewald sphere is rotated
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Reciprocal lattice of polycrystalline sample
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Features of Rigaku TTRAX Ⅲ
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