Electrical and mechanical properties of core-shell type structures in doped BaTiO3

Ferroelectric, core-shell type structures consisting of grains having a diffuse shell and a well defined ferroelectric core, have been developed. These materials were processed in such a way as to: (1) yield a gradient in dopant concentration through each grain, generating either a highly doped shell with a virtually dopant free core, or a uniformly modified grain interior; or, (2) generate a core-shell material, with a gradient from dielectric to semiconductor behavior through the material thickness. These type microstructures, derived from controlled isovalent (ZrO₂) and/or aliovalent (Y₂O₃, Nd₂O₃) doping of the base BaTiO₃ material, were investigated for use as sensors, high strain response materials and high permittivity capacitors. Characteristic of these materials is a stress gradient in the grain, controlled by dopant inhomogeneity, creating a clamping of either the dielectric, resistance or piezoelectric properties