Thermal Diffusion of Injected Impurities into Ceramic Dielectrics

Abstract

First, sintered ceramics of BaTiO3, CaTiO3, Pb(Ti, Zr)O3, and TiO2 were prepared by the conventional method. Then, the disks were coated with powders of metal oxide or carbonate such as CuO, Bi2O3, La2O3, PbO, Co2O3, Cr2O3, Fe2O3, MnCO3 and SrCO3. The injection of various impurities by thermal diffusion were made by heating the ceramice at 1100°-1450°C for 0.5-4h. For these specimens, diffusion depth of the injected impurities into the base ceramics, distribution patterns of the impurities in the ceramics, and effects of the impurities on the electrical properties of the ceramic dielectrics were examined systematically. Main results obtained are summarized as follows.1) Ceramic dielectrics with injected impurities by means of thermal diffusion show properties differing from those with impurities added during the powder stage of the conventional ceramic technique.2) The distribution patterns of the injected impurities were examined by X-ray microanalyzer for CaTiO3 semiconducting ceramic with the injected bismuth oxide, TiO2, ceramic with the injected copper oxide, and BaTiO3 ceramic with the injected manganese oxide. As a result, it was ascertained that the injected impurities were located at the grain boundaries.3) By modifying the characteristics of the grain boundaries by means of thermal diffusion of the injected impurities, we can control the electrical and piezoelectric properties of ceramic dielectrics such as the electromechanical coupling coefficient of BaTiO3 ceramic or the propagation characteristics of surface wave on the PZT ceramic.