The Evaluation of Quartz Resonators Via X-Ray Diffraction Topography

While quartz resonators have been the mainstay of the ultrasonics industry for some time, intricacies exist in the production of quality resonators and therefore fabrication remains somewhat of an art form. Recently the Johns Hopkins University Center for Nondestructive Evaluation has initiated a research program to investigate methods to analyze quartz single crystals for the purpose of assessing the relative crystal quality of the raw material as well as material which has been manufactured into resonators. One technique which has proven to be useful in a variety of single crystal inspection applications is x-ray diffraction topography. X-ray diffraction topography is the name given to several x-ray diffraction techniques which permit the imaging of strains and lattice misorientations associated with surface and internal defects as small as dislocations to be examined. Because the topographic techniques are based on Bragg diffraction from a periodic crystal, the images are extremely sensitive to crystal imperfections, strains, and rotations since any alteration to the interplanar position and spacing of the crystal will effect a corresponding change in the Bragg condition. The dynamical theory of interactionbetween transmitted and reflected wave fields at, or near to, the Bragg condition is intimately connected with spatial contrast in the topographic images. This paper describes experimental details of the x-ray diffraction topographic system used and shows topographic images illustrating the utility of the system as applied to quartz crystals in raw material and resonator form