Abstract
Two groups of PbZrO3 crystals were studied. One exhibited an intermediate rhombohedral ferroelectric phase; in the second this phase did not occur. Flat and crystallographically prominent phase boundaries were observed only in the crystals which exhibited a direct transition from the cubic to the orthorhombic phase. The observed relationships were interpreted in terms of the Roitburd theory. Additional lines were found to occur in the diffraction diagram of the crystals with the intermediate ferroelectric phase.