Impact of Free Charges on Polarization and Pyroelectricity in Antiferrodistortive Structures and Surfaces Induced by a Flexoelectric Effect

Landau-Ginzburg-Devonshire theory has been used to show that the combined effect of flexoelectricity and rotostriction can lead to a spontaneous polarization and pyro-electricity in the vicinity of antiphase boundaries, structural twin walls, surfaces, and interfaces in the octahedrally tilted phase of otherwise non-ferroelectric SrTiO3. In particular, the spontaneous polarization reaches the values similar to 0.1-5 mu C/cm(2) at the SrTiO3 antiphase boundaries and twins without free charges. In the current study we consider the contribution of free charges and show that the spontaneous polarization reaches the values similar to 1-5 mu C/cm(2) in the case. Pyroelectric coefficients also strongly increase allowing for the free charges.