Evidence for a non-rhombohedral average structure in the lead-free piezoelectric material Na0.5Bi0.5TiO3

The potential lead-free piezoelectric material sodium bismuth titanate, Na0.5Bi0.5TiO3, was investigated by means of high-resolution single-crystal X-ray diffractometry. The splitting of Bragg peaks observed in the high-resolution reciprocal-space maps suggests that the average structure of Na0.5Bi0.5TiO3 has lower than rhombohedral symmetry. This observation is contrary to the commonly adopted model, which has followed from many previous analyses of neutron and X-ray powder diffraction data.