THE CORE-SHELL STRUCTURE IN ULTRAFINE X7R DIELECTRIC CERAMICS

Based on a hydrothermal barium titanate powder, temperature stable die lectrics which meet the X7R specification were developed for the use o f Multilayer Capacitors (MLCs). By establishing a chemical inhomogenei ty within individual grains the ferroelectric to paraelectric transiti on peak is diffused and the material has a unique core-shell microstru cture with a pure or lightly doped ferroelectric core and a highly dop ed paraelectric shell. As dielectric layers in MLCs decrease in size s o does the grain size. This study investigates the sintering mechanism and core-shell structure in submicron grains.