Study of defects and structure in organic crystals of potassium hydrogen phthalate

Abstract

Imperfections in the (100), (010) and (001) plates of potassium hydrogen phthalate (KC8H5O4) crystals, cut from various growth zones in different blocks, have been studied by means of X-ray diffraction topography. The experimental results show that there are mainly grown-in dislocations with the Burgers vector b = [100], [110], [1{\bar 1}0] and [101], inclusion-induced dislocations with b = [100] and 〈110〉, glide dislocations in the systems of (001) [1{\bar 1}0], (010) [110] and (010)[1{\bar 1}0], a stacking fault with fault vector R = ± 1/3[20{\bar 1}] and fault plane (1{\bar 2}2), growth layers mostly parallel to 〈111〉 faces, and aqueous inclusions. The dependence of the defect formation on the open structure of the crystal is discussed on the basis of the structure. The variation of the glide-dislocation contrast with wavelength, obtained using synchrotron-radiation section topography, is also given. An inclusion-probed method has proved to be powerful for determining the nature of the strains with large areas caused by thermal action, through study of the black-white contrast variation of inclusions in different strained regions.