Mechanism of ferroelectric properties of (BaCa)(ZrTi)O<inf>3</inf> from first-principles calculations

Electronic, structural, and ferroelectric properties of (BaCa)(ZrTi)O3 (BCZT) were calculated using first-principles calculations and phenomenological Landau-Ginsburg-Devonshire theory. Analysis of relaxed structure and electron charge density shows that the substitution produces different distortion of [TiO6] octahedral at the different site. The double-well potential curve is well fitted by the phenomenological Landau-Ginsburg-Devonshire model. The double-well potential curve is converted to single-well curve with increasing temperature, revealing the ferroelectric-paraelectric phase transition. The spontaneous polarization and well depth of BCZT are reduced in comparison with pure BaTiO3 ferroelectric, which is originated from the squish of Ca ions on the [TiO6] octahedral and the smaller Zr ionic displacement. Analysis of density of states shows that the strong hybridization between Ti 3d and O 2p orbitals and the strong hybridization between Zr 4d and O 2p orbitals are the origin of the ferroelectricity of BCZT materials