A [100] twist low-angle grain boundary in SrTiO3 was systemically studied by means of conventional transmission electron microscopy, high-resolution transmission electron microscopy, lattice distortion analysis, and electron energy-loss spectroscopy. A dislocation network was formed in the grain boundary by two sets of a <100> screw dislocations. High-resolution transmission electron microscopic images showed that the image contrast in the core region was different from that in the surrounding bulk. Image analysis revealed that compared with an ideal screw dislocation the dislocation core was expanded, probably due to both surface relaxation and a reconstruction of the core. The electron energy-loss spectra exhibited a small increase of the Ti/O ratio but no significant change of the Sr/Ti ratio in the core region. From the increase of the Ti/O ratio it was concluded that the dislocation cores were O deficient, which may be responsible for the expansion of the core. Ti L2,3 electron energy-loss spectra exhibited a reduction of Ti in the screw dislocation cores as well as a reduced crystal field splitting, both of which were in accordance with a loss of oxygen.

HRTEM and EELS Study of Screw Dislocation Cores in SrTiO3. Z.Zhang, W.Sigle, W.Kurtz: Physical Review B, 2004, 69[14], 144103 (7pp)