Crystal structure and ferroelectric polarization of tetragonal (Bi1/2Na1/2)TiO3-12BaTiO3

We have investigated the crystal structure and ferroelectric polarization of (Bi1/2Na1/2)TiO3-12%BaTiO3 by high-resolution neutron powder diffraction Rietveld analysis and density-functional theory calculations. It is revealed that the sample has a ferroelectric distortion in tetragonal P4mm symmetry along with a large tetragonality c/a of 1.022. The A- and B-site atoms exhibit a cooperative off-center displacement along the polar c-axis, which results in a large spontaneous polarization of 54 µC/cm2.