FORMATION OF EDGE DISLOCATION DIPOLES IN ICE SINGLE-CRYSTALS BY HEAT-TREATMENT

The behavior of dislocations in artificially-grown single crystals of ice during heat treatment, mainly cooling from various annealing temperatures to a certain low temperature, was examined by X-ray diffraction topography. It was found that edge dipoles were formed from screw dislocations of the frac(1)(3) <112;0> Burgers vector lying on the (0001) plane. Their number, length, and configuration strongly depended upon the initial annealing temperature and the cooling rate. The formation of such dipoles was interpreted in terms of the climb of superjogs on screw dislocations owing to the vacancy supersaturation caused by cooling. If we assume that high superjogs exist intrinsically on grown-in dislocations in ice, the vacancy supersaturation expected in specimens cooled under the experimental conditions could be sufficient to extend them to edge dipoles. Various configurations of the dipoles were interpreted. © 1979 The Japan Society of Applied Physics.