Dense dielectric ceramics with local graded structure from core-shell particles: preparation and properties

摘要

The modification of the surface properties of particles by coating with a different material, resulting in the formation of core-shell structures, is a well-known process. However, the consolidation of core-shell particles in bulk ceramics has not been extensively investigated yet, mainly because of the difficulty in controlling interdiffusion and interface reactions. In this study, we have coated BaTiO(3) spherical templates with SrTiO(3) and BaZrO(3) using a precipitation process from inorganic precursors. The size of the particles as well as the overall composition can be tailored over a wide range. Densification of the resulting core-shell particles was accomplished either using conventional sintering or spark plasma sintering. Dense ceramics with a graded composition at the level of the single grains could only be obtained by careful choice of the sintering conditions. The final ceramics show strongly modified dielectric properties in comparison to both the parent compounds and the homogeneous solid solutions. The proposed approach is quite generic and suggests new possibilities for the realization of polycrystalline materials with local graded structure by the controlled sintering of core-shell particles.