Order-Disorder Behavior in the Phase Transition of PbTiO₃


We have quantitatively measured the temperature dependence of the local distortions of PbTiO3, crystals below and above the structural ferroelectric phase transition using X-ray Absorption Fine Structure (XAFS) measurements. Both Pb and Ti edges were measured, providing quantitative determinations of the displacements of the atoms within the unit cell. These distortions vary little with temperature below the transition and decrease only slightly above the transition temperature. In the paraelectric phase, the Pb and Ti distortions are about 50% and 70% of the corresponding low temperature values respectively. These results show that an essential element of order-disorder is present even in this ferroelectric crystal which displays the soft mode behavior and a dielectric constant typical of displacive ferroelectrics. The presence of the local distortions suggests that the displacements should have at least two correlation length scales, one associated with the local distortions, the other with the order parameter.


Materials Science and Engineering

Keywords and Phrases

Lead titanate; X ray absorption fine structure (XAFS); Correlation methods; Crystals; Lead compounds; Order disorder transitions; Permittivity; Thermal effects; Titanium oxides; X ray analysis; Ferroelectric materials

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Document Type

Article - Journal

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© 1995 Taylor and Francis, All rights reserved.

Publication Date

01 Feb 1995