Influence of core-shell structured grain on dielectric properties of cerium-modified barium titanate

The dielectric properties and chemical inhomogenity of BaTiO3, ceramics sintered with additions of CeO2:1.5TiO(2) were investigated using TEM XRD and EDS. Grains had three regions: grain shell severely doped with cerium, grain core BaTiO3 of greater purity, and a concentration gradient region where Curie temperatures were distributed. With decreasing temperatures, the volume fraction of ferroelectric domains in the concentration gradient region increased. Addition of CeO2:1.5TiO(2) to BaTiO3 decreased the tetragonality (cia ratio) and the grain size, and lowered the Curie temperature by approximately 30 degrees C per mol%. Even a small addition of 0.005 mol CeO2:1.5TiO(2) to BaTiO3 reduced the average grain size from 25 mu m to less than 1.25 mu m and grains of an average grain size were completely doped with cerium, which explained why the 130 degrees C ferroelectric transition peak did not exist. The inhomogenity of the cerium concentration had a large influence on the dielectric temperature characteristic.