First-principles study of ferroelectric and piezoelectric properties of tetragonal SrTiO3 and BaTiO3 with in-plane compressive structures

Ferroelectric and piezoelectric properties of tetragonal SrTiO3 and BaTiO3 with in-plane compressive structures have been investigated using a first-principles calculation. It has been found that the ferroelectric structure appears even in SrTiO3 with in-plane compressive structures. The piezoelectric constant e 33 drastically increases in SrTiO3 rather than that in BaTiO3 as the tetragonal ratio c / a (>1) is close to 1. On the other hand, e 31 shows negative in SrTiO3 while positive in BaTiO3, although the changes in their absolute values are very small. We have found that these properties of e 33 and e 31 in SrTiO3 and BaTiO3 are closely related to the ionic distances.