DISLOCATION REACTIONS AND CAVITATION STUDIES IN MELT-GROWN SAPPHIRE

The veiled region in Czochralski sapphire has been examined for defects by optical micrography, scanning electron microscopy, electron microprobe analysis and X-ray topography. High optical scattering in the veiled region is found to be due to a large number of cavities. Some dislocation reactions have been observed in the X-ray topographs. High strain fields associated with cavities are also revealed by the topographs indicating that they contain entrapped gas at high pressure. This pressure is three orders of magnitude greater than that predicted from surface tension considerations. © 1969 Chapman and Hall.