The University of Arizona

Scintag XDS 2000

a picture of the Scintag XDS 2000

The phenomenon of diffraction occurs when penetrating radiation, such as X-rays, enters a crystalline substance and is scattered. The direction and intensity of the scattered (diffracted) beams depends on the orientation of the crystal lattice with respect to the incident beam. Any face of a crystal lattice consists of parallel rows of atoms separated by a unique distance (d-spacing), which are capable of diffracting X-rays. In order for a beam to be 100% diffracted, the distance it travels between rows of atoms at the angle of incidence must be equal to an integral multiple of the wavelength of the incident beam. D-spacings which are greater or lesser than the wavelength of the directed X-ray beam at the angle of incidence will produce a diffracted beam of less than 100% intensity.

Our diffractometer utilizes a powdered sample, a goniometer, and a fixed-position detector to measure the diffraction patterns of unknowns. The powdered sample provides (theoretically) all possible orientations of the crystal lattice, the goniometer provides a variety of angles of incidence, and the detector measures the intensity of the diffracted beam. The resulting analysis is described graphically as a set of peaks with % intensity on the Y-axis and goniometer angle on the X-axis. The exact angle and intensity of a set of peaks is unique to the crystal structure being examined. In a multi-component mixture, confusion can arise when two or more components have a peak in the same, or nearby, location on the X-axis. It is for sorting out these mixtures that a good search/match engine or a search method becomes most important.

The X-Ray diffraction method is most useful for qualitative, rather than quantitative, analysis (although it can be used for both).

XRD Data
Two different phases of TiO2

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University Spectroscopy and Imaging Facilities