A TEM study of grain boundaries in internal boundary layer capacitors based on donor-doped (Sr, Ca) TiO3 ceramics

Donor-doped (Sr, Ca)TiO3 ceramics, either oxidized or infiltrated by Bi2O3 and Bi2O3-PbO molten mixtures, have been studied using a transmission electron microscope equipped with EDX facilities. Grain boundary morphologies of these different materials are investigated. In oxidized samples, grain surfaces exhibit a chemical contrast, interpreted as the result of a TiO2 segregation that occurs during the sintering stage. Moreover, the in-detail characterization of infiltrated specimens reveals that intergranular regions present a facies strongly influenced by the type of mixture used. During the infiltration step, grains are slightly dissolved by molten oxides and Pb noticeably enhances this process.