Superlattice in single crystal barium-doped sodium bismuth titanate Original Research Article

Na1/2Bi1/2TiO3 (NBT) doped with BaTiO3 (BT) has recently shown promising piezoelectric properties in single crystal form. The piezoelectric properties appear to be highly dependent on BT concentration, with compositions close to the morphotropic phase boundary (∼6% BT) having the highest piezoelectric coefficients. Previous studies have resulted in conflicting conclusions regarding the presence and nature of the superlattice in NBT. Using HREM and hot-stage TEM electron diffraction, we show that flux-grown single crystals of compositions (1−x)NBT–xBT with x<0.08 exhibit superlattice reflections that are present from room temperature up to 500°C, above which temperature they reversibly vanish. The reflections are consistent with a superstructure due to single-axis in-phase octahedral tilt (a0a0c+). The dependence of the superlattice reflection intensity on temperature and BT content as well as possible mechanisms of superlattice formation are discussed.