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A [001](110) small-angle grain boundary SrTiO 3 was studied by electron-energy-loss spectroscopy (EELS) and high-resolution transmission electron microscopy. The a< 110> grain boundary dislocations were dissociated into two partial dislocations involving climb of the partials. From their separation an upper limit of the (110) antiphase boundary energy of (720±2 8 0) m J/m 2 is deduced. EELS spectra were obtained from the partial cores and the antiphase boundary in a dedicated scanning transmission electron microscope. The Sr/Ti ratio was found to be increased in one of the partial cores but decreased in the other. This can be understood from the dissociation mechanism. From the increase of the Ti/O ratio it is concluded that the dislocation cores are oxygen deficient. Ti− L 2, 3 EELS spectra show a reduction of Ti in the partial dislocation cores as well as a reduced crystal field. Atomic models of the …