Electron Microscope Study of Dauphine Microtwins Formed in Synthetic Quartz
AIR FORCE CAMBRIDGE RESEARCH LABS HANSCOM AFB MA
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Specimens of synthetic quartz were examined by transmission electron microscopy. Dauphine twins in 0001 sections, produced by cooling through the inversion temperature, were decorated at the boundaries by black spots caused by radiation damage in the microscope. These boundaries were straight lines following crystallographic directions. A misorientation between twins and matrix accounts for intensity differences between the two regions. The results are compared with those obtained with 1120 sections where fringe contrast at the twin boundary occurs because of differences in extinction distance for certain reflections. Smaller, more numerous twins were formed in electron damaged regions during examination in the microscope.