The tetragonal phase of Na0.5Bi0.5TiO3 — a new variant of the perovskite structure.

The structure of the tetragonal phase of the A-site-substituted perovskite sodium bismuth titanate, Na0.5Bi0.5TiO3, has been determined by neutron powder diffraction of 698 K. The structure was refined in space group P4bm with a (= b) = 5.5191 (1), c = 3.9085 (1) Å, V = 119.055 (5) ų, Z = 2 and Dx = 5.91 Mg m-3. The structure exhibits an unusual combination of in-phase (a0a0c-) tilts and antiparallel cation displacements along the polar c axis, which results in a new variant of the perovskite structure. [ABSTRACT FROM AUTHOR]