Interfacial Polarization and Pyroelectricity in Antiferrodistortive   Structures Induced by a Flexoelectric Effect and Rotostriction
  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 
Anna N. Morozovska, Eugene A. Eliseev, Maya D. Glinchuk, Long-Qing   Chen, and Venkatraman Gopalan
cond-mat.mtrl-sci