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Phase identification

Phase Identification

Powder diffraction data are commonly used to identify or ‘finger print’ crystalline materials. An international database was started in the 1930s and is regularly updated.

In its simplest form, PDF1 (powder diffraction file) lists d-spacings and relative intensities. Most data are now indexed and so include cell parameters, the chemistry, density and other properties of the material. This is called PDF2. It is maintained by ICDD (International Centre for Diffraction Data) formerly JCPDS (Joint Committee for Powder Diffraction Standards).

To identify a particular phase both peak positions and relative intensities must fit. In general this requirement should hold for at least three peaks. Below are two examples of how this process works. The first one is a simple purity check on hydroxyapatite and the second a more complex example identifying three possible phases in stabilised zirconias. Similar logic applies to completely unknown samples.

Note: This animation requires Adobe Flash Player 8 and later, which can be downloaded here.

Note: This animation requires Adobe Flash Player 8 and later, which can be downloaded here.


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