90°-domain wall relaxation in tetragonally distorted ferroelectric ceramics

A phenomenological model of a vibrating 90°-domain wall in an electric and mechanic stress field is presented. The model allows to separate the domain wall and the volume contribution to the complex dielectric, piezoelectric and elastic constants. The results are compared with representative measurements of the above mentioned six material parameters on a Fe-doped PZT sample. It turns out that the absolute values and the temperature dependencies of the intrinsic contributions are comparable to those obtained by a thermodynamical treatment. The ratio S0/P0 (spontaneous deformation/spontaneous polarization) which can also be derived in our model from the measured losses, is in good agreement with other measuring methods. It follows that, although there is as yet no physical interpretation for the loss mechanism, the conception of a vibrating 90°-domain wall under the above described conditions is a useful path towards a better insight into the material properties of ferroelectric ceramics.