Crystal Structure 1 3.1 Some Basic Concepts of Crystal Structure ...

Crystal Structure
Powder Diffraction
In this method, the specimen is in a powder form hence contains a large number of
crystallites in random orientation. The x-ray used is monochromatic. Fig. 3.24 shows the
schematic diagram of the setup and a powder diffraction pattern from ZnO. A set of
atomic planes with spacing d will give rise to a diffracted beam at an angle 2 (with
respect to the incoming direction of the incident x-ray) according to the Bragg law. Since
the orientation of the crystallites is random, the diffracted beam can at any azimuthal
direction. The diffracted beams will spread around the surface of a cone with the apex at
the specimen.
Bragg Diffraction and Reciprocal Lattice Vectors
Fig. 3.24 Schematic diagram of the setup for the powder diffraction method, and a powder pattern
obtained from a ZnO sample.
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