Influence of the piezoeffect on static and dynamic ferroelectric properties

Abstract

Typical ferroelectric properties like polarization hysteresis and a phase transition from ferroelectric to paraelectric at the Curie temperature can be deduced from the Weiss field model. This model is based on a feedback loop where the polarization influences itself by the electrostatic interaction between the dipoles inside the material. An extension of this model considers that the strain due to the piezoelectric effect changes the lengths of the dipoles inside the sample. In this extended model, a positive piezocoefficient converts the second order to a first order phase transition and splits simultaneously the single polarization hysteresis loop to a double loop close to the Curie temperature. The same behaviour we find for negative piezocoefficients if the piezoelectric effect influences the dipole density of the sample or the coupling between the dipoles instead of the dipole lengths. The dependence of the electrode distance on the polarization due to the piezoeffect has only small influence on the polarization hysteresis and the coercive field below the Curie temperature; remanent polarization or order of the phase transition is not changed. Furthermore, dynamic simulations show the effect of the velocity of temperature and external voltage variation on the polarization.