Fabrication and characteristics of fine-grained BaTiO3 ceramics by spark plasma sintering

Abstract Fine-grained BaTiO3 ceramics were obtained at a low sintering temperature of 900 °C within a short sintering period by means of a new sintering method-spark plasma sintering (SPS). The ceramics are highly densified to more than 99% of the theoretical X-ray density with homogeneous microstructures, signifying that the SPS process is effective for the densifying of compacts and the inhibition of exaggerated grain growth. Nanocrystalline BaTiO3 powder of 13 nm grain size was used as the starting material. Observations of pellets by HRTEM indicated that the grains only support 180° domain structures and in some cases unusual twins were discovered. XRD measurement shows that in fine-grained SPS pellets a small amount of cubic phase is present. A clear dependence of the dielectric constant on grain size was observed. It is believed that the existence of twins is one of the key factors that resulted in the slight decrease of the dielectric constant of fine-grained ceramics.