NEUTRON-DIFFRACTION

A brief account is given of neutron diffraction techniques. Similarities and differences compared with the more familiar X-ray counterparts are discussed. In certain applications, neutron diffraction can be used to obtain information about materials which would be difficult or even impossible to obtain using other techniques. One spectacular success has been the elucidation, from neutron powder diffraction, of the crystal structures of high critical temperature oxide superconductors. There have been substantial contributions in other fields, and these are illustrated by Australian work. The ability of the neutron to penetrate deeply into most materials has been invoked for in-depth determination of stresses in composites and of phase composition in zirconia ceramics. The unique properties of the neutron have been successfully exploited in studies of metal hydrides, to determine where hydrogen is located, and in magnetic structure determination. There is much interest in studying materials under different conditions of temperature and pressure, and kinetic studies under such conditions are now becoming possible. The article includes information on the principles, the instrumentation with particular reference to the instruments installed around the HIFAR reactor at Lucas Heights, and methods for the interpretation of data. The instrumentation has been substantially improved and, given an increasing awareness in the materials science community of the capabilities of neutron diffraction, an increasing number of applications is expected.