Antiferroelectric phase transition and order parameters of PbZrO3

Powder X-ray diffraction experiments of the antiferroelectric PbZrO3 were performed between room temperature and 8K. Temperature dependence of the antiferroelectric superlattice-reflection intensities shows a rapid saturation below 60K. The dependence is discussed by a conventional and a quantum expansion of a phenomenological theory. Superlattice-reflection intensities caused by R-25 mode were found to show the same dependence on temperature as the antiferroelectric superlattice-reflections below room temperature, though they show different dependence above room temperature. The tetragonal lattice distortion of the perovskite sublattice shows the same dependence on temperature as that of the antiferroelectric superlattice reflections. The distortion in ab plane was found to show the temperature dependence being well expressed by a sum of the linear and the quadratic terms of the antiferroelectric superlattice reflections. Lattice distortions and a topology of order parameter vector space are discussed by a phenomenological theory using a group theoretical method.