Atomic structure of undoped Σ=5 symmetrical-tilt grain boundary in strontium titanate

Strontium titanate is an important electroceramic material which, under appropriate processing and dopant additions exhibits both varistor and Grain Boundary Layer Capacitor (GBLC) behavior. The presence of electrically active grain boundaries is essential for obtaining these properties. The first step towards correlating the grain boundary structure to properties is to determine the detailed atomic structure of the boundary, which includes its geometric structure, chemistry and electronic structure. We present here our TEM investigation of the atomic structure of an undoped (“pristine”) symmetrical tilt grain boundary in SrTiO3. This provides the basic reference structure, changes to which can be studied as a function of doping and/or processing parameters, and correlated to electrical and dielectric properties.Self-supported TEM samples were made from bicrystals of SrTiO3 through the conventional sample preparation route. Fig. 1 shows a high resolution electron micrograph (Hitachi H9000) of a representative grain boundary region in the sample.