  Theoretical analysis based on the Landau-Ginzburg-Devonshire (LGD) theory is
used to show that the product effect of flexoelectricity and rotostriction can
lead to a spontaneous polarization in the vicinity of antiphase boundaries,
ferroelastic twin walls, surfaces and interfaces in the octahedrally tilted
phase of otherwise non-ferroelectric perovskites such as CaTiO3, SrTiO3, and
EuTiO3. As an example, we numerically demonstrate a large spontaneous
polarization on the order of 1-5muC/cm2 at the SrTiO3 antidistortive phase
boundaries at temperatures lower than the antiferrodistortive structural phase
transition temperature of ~105 K
