The influence of grain boundary on the conductivity of donor doped SrTiO3

The electrical conductivity of polycrystalline Sr(Ti0.999Nb0.001)O3 was investigated. The conductivity was smaller by 1–2 order than that of the single crystal. The conductivity increased with temperature with the activation energy of 0.61 eV. The distribution of grain boundary nature of the polycrystalline sample was determined by Orientation Imaging Microscope (OIM) analysis. The ratio of coincident lattice boundaries was determined to be approximately 20%. The impedance of bicrystals across the grain boundary with different grain boundary type was measured. The grain boundary impedance was found to consist of two RC parallel components in series. The activation energies of them were 0.56–0.71 eV and 1.73–1.97 eV, respectively. These two processes were assigned to the grain boundary or annealed surface layer and the Schottky barrier between the bulk and the surface or the grain boundary layer. A possible conduction mechanism of polycrystalline material was considered that of the three dimensional network of the grain boundary layer.