Formation of Core‐Shell Structure in Ultrafine‐Grained BaTiO3‐Based Ceramics Through Nanodopant Method

The formation of core‐shell structure is the key issue of temperature stable barium titanate‐based dielectric ceramic for multilayer ceramic capacitor application. It is difficult to obtain and observe the core‐shell structure in ceramic grains when the grain size becomes smaller, especially to sizes <200 nm. A nanodopant method has been developed for the preparation of ultrafine‐grained barium titanate‐based ceramics with grain size below 200 nm. The existence of core‐shell structure was proved by transmission electron microscopy observation and energy‐dispersive spectroscopy analysis. High‐performance X7R dielectric ceramics were produced in a reducing atmosphere by normal sintering and two‐step sintering method. The dielectric constant at room temperature could reach over 2000, with a low dielectric loss at about 1.0% and high insulation resistivity ∼10 12 Ω·cm.