Microstructural observations of flux-sintered barium titanate

Abstract

High permittivity materials are usually based on BaTiO3 and other Perovskite systems. Hetero-substitution of Ca, Pb, Zr, and Sn provide the necessary control in selection of suitable dielectric constants, temperature-resistance coefficients and dielectric losses. However, preparation of these materials require sintering temperatures in excess of 1300°C and often extended sintering times. Lower sintering temperatures are economically favorable and commercially important in monolithic capacitor fabrication, since they allow the use of base metal electrode systems such as Ni or Cu, replacing the more expensive Ag-Pd systems now employed. The approach has been to lower the sintering temperature of the dielectric by small additions of fluxing agents such as LiF and borates, which promote liquid phase sintering. By sintering in the presence of a liquid, densities approaching theoretical can be achieved at significantly reduced densification temperatures and times. With the electronic industries trend toward miniaturization, dielectrics with a high dielectric constant and low sintering temperature offer a significant advance in packaging density.