X-ray diffraction topography study of defects in potassium dihydrogen phosphate (KDP) and ammonium dihydrogen phosphate (ADP) single crystals

The direct observation of dislocations in KH₂PO₄(KDP) and NH₄H₂PO₄ (ADP) single crystals has been performed by X-ray diffraction topography methods. Crystals were grown by slow cooling of stirred solutions on different types of seed crystals. It is demonstrated that the main sources of dislocation generation are the seed surface, inclusions of mother liquor and foreign particles. Space orientation of dislocations and their Burgers vector directions are found. In regions far from the seed the dislocation density did not exceed 10³ cm⁻² and a number of specimens with cross-sectional areas up to several cm² were free from dislocations. Dynamical phenomena characteristic of the diffraction in a weakly deformed lattice have been observed over a wide range of μ t at the boundaries between the {101} and {100} growth sectors having different impurity contents. Several crystals show also nonuniform impurity distribution in the form ot the layers parallel to growing face (growth layers).