2.6 X-Ray Diffraction Methods Method Laue Rotating Crystal Powder Orientation Lattice constant Lattice Parameters Single Crystal Single Crystal Polycrystal (powdered) Polychromatic Beam Monochromatic Beam Monochromatic Beam Fixed Angle Variable angle Variable angle
2.6 X-Ray Diffraction Methods Method Laue Rotating Crystal Powder Orientation Single Crystal Polychromatic Beam Fixed Angle Lattice constant Single Crystal Monochromatic Beam Variable Angle Lattice Parameters Polycrystal (powdered) Monochromatic Beam Variable Angle
Crystal diffraction experimental methods a)Laue method:continuous X ray for a single crystal Sample X-ray source Collimator Forward Back ditfraction reflection plate plate position position Goniometer mount
Crystal diffraction experimental methods a) Laue method: continuous X ray for a single crystal
FeS2:two crystal phases 0 1( Figure 1-38 Laue X-ray diffractionspotpatternsfor(100)and(110)orientations with respect to pyrite (FeS)single crystals.(Photos courtesy of L.E.Murr,Oregon Graduate Center.)
FeS2 : two crystal phases
Laue Patterns The symmetry of the Laue spot pattern reflects the symmetry of the crystal when viewed along the direction of the incident beam. Laue method is often used to determine the orientation of single crystals by illuminating the crystal with a continous spectrum of X-Rays. Single crystals Continous spectrum ofX-Rays Symmetry orientation ofcrystals
• The symmetry of the Laue spot pattern reflects the symmetry of the crystal when viewed along the direction of the incident beam. Laue method is often used to determine the orientation of single crystals by illuminating the crystal with a continous spectrum of X-Rays. Single crystals Continous spectrum of X-Rays Symmetry & orientation of crystals Laue Patterns
b)Debye-Scherrer method Constant wavelength for powders X ray tube Diffraction cone Collimator Powder sample Useful for samples that are difficult to obtain in single crystal form.The powder method is used to determine the lattice parameters accurately a,b and c
b) Debye-Scherrer method Constant wavelength for powders Useful for samples that are difficult to obtain in single crystal form.The powder method is used to determine the lattice parameters accurately a, b and c