Effects of growth rates on the defect generation in KCl crystals grown by the czochralski method

The effects of the growth rates on the perfection of KCl crystals grown by the Czochralski method were investigated in the range of the pulling rate from 1 to 27.3 mm/hr using the etch pit method. It was found that the density of random dislocation within subgrains was almost independent on the pulling rate but the length of subboundaries in the unit area was decreased with an increase of the pulling rate. The shape of the solid‐liquid interface changed from convex towards the melt to flat with an increase of the pulling rates. It was found that the leading factor in producing subboundaries is the shape of the solid‐liquid interface, and that the pulling rate alone does not always determine the perfection.