Modulation of a crystal lattice in Na1/2Bi1/2TiO3 (NBT) crystal

The diffuse neutron scattering in NBT monocrystal related to the correlation of oxygen octahedra tilting is studied. It is shown that the competition between the M3 and R25 order parameters results in the appearance of a lattice modulation under the transition from a tetragonal to a rhombohedral phase. These results are confirmed by the measurements on the single domain crystal. The observed modulation is probably concerned with the existence of the antiphase domains of the phase with the R25 order parameter separated by the domain walls of the phase with the M3 order parameter. 8 refs.; 7 figs