Introduction

Powder x-ray diffraction (XRD) uses x-rays to investigate and quantify the crystalline nature of materials by measuring the diffraction of x-rays from the planes of atoms within the material. It is sensitive to both the type of and relative position of atoms in the material as well as the length scale over which the crystalline order persists. It can, therefore, be used to measure the crystalline content of materials; identify the crystalline phases present (including the quantification of mixtures in favourable cases); determine the spacing between lattice planes and the length scales over which they persist; and to study preferential ordering and epitaxial growth of crystallites. In essence it probes length scales from approximately sub angstroms to a few nm and is sensitive to ordering over tens of nanometres.

The samples for analysis are typically in the form of finely divided powders, but diffraction can also be obtained from surfaces, provided they are relatively flat and not too rough. Moreover the materials can be of a vast array of types, including inorganic, organic, polymers, metals or composites and the potential applications cover almost all research fields, e.g. metallurgy, pharmaceuticals, earth sciences, polymers and composites, microelectronics and nanotechnology. Powder XRD can also be applied to study the pseudo crystalline structure of mesoporous materials and colloidal crystals provided that the length scales are in the correct regime.

Through self-instruction, this module will introduce you to:

• The basics of X-Ray diffraction and the forming of powder patterns.

• The instrumentation used to perform X-Ray diffraction.

• How to prepare samples for XRD.

• How to conduct powder XRD experiments.

• How to interpret powder X-Ray diffractograms.

In addition, you will have access to a virtual diffractometer which will enable you to try some simple experiments and visualize their results. The module will assist you to conduct X-Ray diffraction experiments and interpret their results. However, it will NOT turn you into a fully-fledged expert overnight; that requires a lot of experience.