THE INFLUENCE OF MICROSTRUCTURE ON THE PROPERTIES OF FERROELECTRIC CERAMICS

The domain twinning in ferroelectric ceramics is dependent on grain size. In fine grained ceramic a simple lamellar structure allows two- dimensional stress relief, in coarse grained ceramic a banded lamellar structure takes away homogeneous stress in three dimensions. The different domain configurations and internal stresses lead to different dielectric properties and to different hysteresis curves. Inhomogeneous grains of BaTiO, with some CdBi,Nb,O,. have a core with a normal domain pattern and a shell without domains at room temperature. Core and shell have different transition temperatures. The macroscopic dielectric constant therefore has very high values in a very broad temperature range. Ceramics which are properly prepared in order to have oriented grains exhibit properties which come near to the properties of single crystals. © 1990, Taylor & Francis Group, LLC. All rights reserved.