Growth Characteristics of KCl Single Crystal Effected by High Growth Rate Direction

When KCl is cooled rapidly from the melt, there occurs a complicated crystal growth and several KCl single crystals are obtained in the crucible. The author has studied several properties of the crystal fragments mainly from the macroscopic point of view. In this paper, a model is treated on the morphology of the crystal growth in special reference to the growth only in high growth rate direction, as follows. The propagation of growing surface is analyzed when the melt is solidified under a constant supercooling and a constant cooling rate conditions, and then the periodic steplike growing surface and the spacing between the subgrain boundaries determined by the physical circumstance are examined. The models of the crystal growth condition as approximations of the actual growth are proposed and the propagation of subgrain boundary is also discussed. Furthermore, these results are confirmed by the observation of the crystal.