It has been found that ferroelectric BaTi${\mathrm{O}}_{3}$ single crystals show a differential etch rate when etched in hydrochloric acid. The positive end of the electric polarization etches much faster than the negative one. Thus this phenomenon affords a valuable new tool for the investigation of the ferroelectric domains in BaTi${\mathrm{O}}_{3}$. Some interesting pictures of domain arrangements are shown and discussed. The results obtained demonstrate the extremely strong electric dipole-dipole coupling in the forward direction and the weak coupling in the directions perpendicular to it. This electrostatic interaction governs the domain patterns in ferroelectric BaTi${\mathrm{O}}_{3}$ crystals.
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