Electron diffraction studies of phonon and static disorder in SrTiO3

Three kinds of diffuse scattering associated with phonon and static disorde r in SrTiO3 were studied by electron diffraction with a parallel beam. (1) Streaks of diffuse scattering along the reciprocal lines MRM were found to originate from dynamically correlated rotations of oxygen-octahedra within the (0 0 1) layer and uncorrelated rotation between the layers; when temper ature is lowered to the transition temperature T-c congruent to 103 K, the crystal structure condenses into thin plates of antiphase domains in every orientational variant. (2) Diffuse scattering around the R point, due to th e Gamma(25) phonon mode, becomes weaker and broader with an increase in tem perature and is even detectable at 700 K. (3) Sheets of diffuse scattering in the reciprocal X-Gamma-X-M-X plane result from the correlated movements of atomic chains along the [0 0 1] direction. Structural models are propose d to interpret these diffuse scatterings.