Electron microscope analyses of domains and discommensurations in ferroelectric Rb₂ZnCl₄

Image contrast of domains and discommensurations in ferroelectric Rb₂ZnCl₄ is studied. Six domains of the two orientation variants and three translation variants in the ferroelectric phase are observed. However, only two kinds of domain boundaries, which are the discommensurations in the incommensurate phase of Rb₂ZnCl₄, are observed. These observations agree with group-theoretical considerations of the phase transition from the normal phase to the commensurate phase of Rb₂ZnCl₄.