X-Ray Reflection from Inhomogeneously Strained Quartz

Abstract

Laue spots from quartz crystals undergoing piezo-electric vibrations are found to have a fine structure. The nature of this structure is such as to indicate that the increase of reflecting power of a given crystallographic plane varies greatly from point to point in the crystal, while at a given point in the crystal the reflecting power of different planes is increased in different amounts with a resultant intensity distribution unlike that obtained from a rough-ground surface of the crystal. It is proposed that these effects are due to the existence of strain gradients in the crystal, distributed at random in the rough-ground surface but in definite directions in the case of a vibrating crystal. This view is substantiated by some static tests on inhomogeneously strained crystals. Some specimens of quartz with imperfect interior regions are found to have random strain gradients. The effect on reflected intensity may be accounted for on the basis of a reduction of extinction. The phenomenon is used in the study of modes of vibration of quartz plates.