3. Phase identification

The most important application of powder diffractometry is undoubtedly the identification of the phases present in a sample.

Each crystallized phase presents a unique diffractogram, since the positions of the lines depend on the dimensions of the elementary mesh, and the intensities of the lines depend on the arrangement of the atoms in the crystal. Consequently, each substance or phase can be identified by its characteristic "fingerprint"; with very rare exceptions, two distinct phases have different diffractograms.

Phase identification consists in comparing the diagram of the unknown sample with those of the reference materials known to date. To do this, the lines are listed with their interreticular distances in descending order and their relative intensities, i.e. the pairs d - I. The characteristic part of the diagram is limited to...