Aging of fe-doped pzt ceramics and the domain wall contribution to the dielectric constant

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Abstract
The time dependence of the complex dielectric constant ε of ferroelectric ceramics is well known as aging which is ascribed by most authors to a modification of the 90°-domain walls. Measurement of aging of Fe-doped PZT ceramic (rhombohedral) and Cr-doped BT ceramic (tetragonal), show that aging in these ceramics can be understood as a reduction of vibrating 90°-domain wall areas. This reduction of the domain wall contribution to the dielectric constant can be due either by pinning of parts of 90°-domain walls having high activation energies and/or by an increase in domain sue in time which reduces the total domain wall area. The increase of the domain sue during aging is ascribed to a thermally activated relief of internal stresses just by rearrangement of the domain configuration. The stress relaxes in a logarithmic time law which results from uniformly distributed activation energies between an upper and a lower limit. The measurements allow to distinguish clearly the bulk contribution and the domain wall contribution to the dielectric constant. Undoped coarse grained BT ceramic shows an additional aging process during the first time decades.

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