Crystal structure of 0.96(Na_(0.5)Bi_(0.5)TiO_3)-0.04(BaTi03) from combined refinement of x-ray and neutron diffraction patterns

摘要

High-resolution x-ray and neutron diffraction of (0.96)Na_(0.5)Bi_(0.5)TiO_3-(0.04)BaTiO_3 (NBT-4BT) reveal subtle structural distortions that evidence lower symmetry than allowed in the R3c space group. The combined refinement that best models the diffraction patterns is a two phase mixture of a monoclinic Cc phase and a minor fraction of a metrically cubic Pm3m phase (13 wt. %). The cubic phase is utilized to account for nanometer-scale regions whose local deviations from the long-range symmetry are not observed, such as polar nano-regions or tetragonal platelets. This suggests that the low symmetry found in the NBT-rich phases extends from 0 at. % to at least 4 at. % BT.