Structure, dielectric and ferroelectric anisotropy of Sr2−xCaxBi4Ti5O18 ceramics

Sr2−xCaxBi4Ti5O18(x = 0, 0.05) powders synthesized by solid state route were uniaxially pressed and sintered at 1225 °C for 2 h. The obtained dense ceramics exhibited crystallographic anisotropy with a dominant c axis parallel to the uniaxial pressing direction which was quantified in terms of the Lotgering factor. Microstructure anisotropy of both compositions (x = 0, 0.05) consisted of plate like grains exhibiting their larger surfaces mostly perpendicular to the uniaxial pressing direction. Dielectric and ferroelectric properties of Sr2−xCaxBi4Ti5O18 ceramics were measured under an electric field (E) applied parallel and perpendicularly to uniaxial pressing direction. The obtained dielectric ɛR(T) and polarization (P–E) curves depended strongly on E direction thus denoting a significant effect from microstructure and crystallographic texture. Sr2−xCaxBi4Ti5O18 properties were also significantly affected by Ca content (x): Curie temperature increased from 280 °C (x = 0) to 310 °C (x = 0.05) while ɛR and remnant polarization decreased for x = 0.05. The present results are discussed within the framework of the processing and crystal structure–properties relationships of Aurivillius oxides ceramics.