Elastic diffuse scattering of neutrons as a tool for investigation of non-magnetic point defects

Valuable information on the interatomic forces and energies in solids can be drawn from scattering experiments on crystals containing randomly distributed defects. However, defect concentrations usually have to be kept small to ensure random distribution and this is one of the reasons for a generally low signal. Neutrons can be used with advantage for such investigations if the incoherent-scattering cross section of the host material is small. The particular properties of slow neutrons make it possible to apply a number of experimental methods to obtain the desired information. Variation of incident energy and resolution in momentum space, the use of different isotopes as defects and - in particular if the experiments have to be done at high temperatures - analysis of the energy of the scattered neutrons may help to compensate for the usually low luminosity of neutron sources as compared, e.g., to X-ray tubes. Careful design of the sample's environment and appropriate choice of experimental parameters allow measurements on samples with defect concentrations down to 0.1 at. % and at temperatures up to several hundred Centigrade. Experimental facilities of this type have been installed in Jülich and in Grenoble. The results obtained so far on various alloy systems show that considerable success is possible.