First-principles study of polarization and piezoelectricity behavior in tetragonal PbTiO 3 -based superlattices

Using first-principles calculation, the contribution of A-site and B-site atoms to polarization and piezoelectricity d33 in the tetragonal PbTiO3/KNbO3 and PbTiO3/LaAlO3 superlattices is investigated in this paper. It is shown that PbTiO3/KNbO3 superlattice has larger polarization and d33 than PbTiO3/LaAlO3 superlattice, because there is stronger charge transfer between A(B)-site atoms and oxygen atom in PbTiO3/KNbO3 superlattice. In PbTiO3/KNbO3 superlattice, B-site atoms (Ti, Nb) make larger contribution to the total polarization and d33 than the A-site atoms (Pb, K) because of the strong covalent interactions between the transition metal (Ti, Nb) and the oxygen atoms, while piezoelectricity in PbTiO3/LaAlO3 superlattice mainly ascribes to piezoelectric contribution of Pb atom and Ti atom in PbTiO3 component. Furthermore, by calculating the proportion of the piezoelectric contribution from PbTiO3 component in superlattices, we find there is different response of strain to piezoelectric contribution from PbTiO3 component in two superlattices but still with a value larger than 50%. In PbTiO3/KNbO3 superlattice, the c-axis strain reduces the proportion, especially under tensile condition. Meanwhile in PbTiO3/LaAlO3 superlattice, PbTiO3 plays a leading role to the total d33, especially under compressive condition, and the proportion decreases as the tensile strain increases.