Growth and defects of DAST crystal in high concentration solution

The 4-N,N-dimethylamino-4-N-methyl stilbazolium tosylate (DAST) crystal with large size and nearly square shape was grown in high concentration solution by slope nucleation method coupled slow cooling (SNM-SC). Striations considered as planar defects were found on the (0 0 1) face along a-axis in the crystal by optical microscope. Some of the striations were continuous while some of them were discontinuous. In addition, the striations were found on (2 3 1) diffracting face and such lines did not occur on the (3-21) and (−2 2 1) planes. The surface distribution and morphological structure of the crystal were characterized by XRD and atomic force microscope (AFM). The presence of striations in the sample was also confirmed by white-beam synchrotron radiation topography (WBSRT). The mechanism of striations formation was also discussed.