Characterization of crystals by γ-ray and neutron diffraction methods

Abstract

After a brief description of the characteristic features of neutron diffraction experiments, the emphasis is on the presentation of γ-ray diffractometry as a convenient method for studying the degree of perfection of large ȁas-grownȁ single crystals without the need for cutting or surface treatments. Commercially available 192Ir sources of 200 Ci activity and a half-life of 74.2 day provide sufficiently strong γ-lines at 316.4, 468.0 and 604.4 keV to measure a series of rocking curves in a reasonable amount of time. Because of the weak interaction of this γ-radiation with matter, its mean free path is of the order of 1 cm. Single crystals contained in a large variety of furnaces, cryostats or high pressure cells can be studied easily. In general, the kinematical diffraction theory applies in γ-ray diffractometry so that the measured rocking curves are directly proportional to the mosaic distribution function which generally describes the degree of perfection of imperfect single crystals.