First Principles Investigation of Novel Ferroelectric Perovskite Alloys Based on A-site Substitution

摘要

We report first principles studies of the lattice instabilities of as yet unsynthesized perovskites based on alloys in the (Th,Pb,Ba,Bi,Y)ScO_3 system. These systems are characterized by strong structural instabilies of the cubic perovskite lattice and A-site driven ferroelectricity. Tetragonal ferroelectric structures in these systems are found to show rather large values of the da ratio, which when present near a morphotropic phase boundary are thought to be associated with large piezoelectric actuation. The relationship between octahedral rotational and ferroelectric instabilities is discussed as are the conditions for obtaining a morphotropic phase boundary.