Structural Study of Ferroelectric Phase Transition in Ca₂Pb(C₂H₅CO₂)₆ Crystals

抄録

Ferroelectric phase transition in DLP crystals is studied on the basis of the crystal structure determined at various temperatures above and below the phase transition temperature. Temperature variation of the atomic order parameter of methyl groups is determined. In contrast to the disordered character in the CH₃ groups, the ionic atoms; Pb, Ca and O, which bear the major part of spontaneous polarization, exhibit no disordered character in both phases. It is pointed out that the disordering in the CH₃ groups is by no means strongly correlated with motions of ionic atoms in view of quite a special atomic arrangement of DLP. We discuss that this weak coupling between two structural parts leads to the well known peculiar nature of the DSP-type crystals.