Direct observation of dislocations in magnesium oxide

Abstract

Dislocations have been observed in thin metal foils by electron transmission microscopy for a number of years. We have recently observed directly the motion of dislocations in thin crystals of magnesium oxide, a ceramic material of high melting point. Large crystals, supplied by the Norton Company, were prepared by cleavage followed by chemical polishing, to produce a thin specimen. From the measured separations of the traces of (110) slip planes on the two surfaces of the specimen the thickness was found to be 3000 to 5000 Å.