Surface physical studies of barium titanate ceramics

The electric conductivity of barium titanate ceramics and its temperature dependence are strongly related to grain structure and dopant concentration. First results of a systematic study using surface physical techniques are presented starting with undoped ceramic samples. The samples were sintered and treated according to our experiences with single crystalline barium titanate. Scanning electron microscopy and atomic force microscopy (AFM) contact mode images of these samples revealed the grain structure and the surface of the grains. A heavily faceted surface was found on the polished and unpolished sample. The surface structure of the polished sample indicates the orientation of the grains. Additional current images taken in AFM contact mode reveal differences in conductivity of individual grains as well as particular insulating segregations on some parts of grain surfaces.