Superlattice in single crystal barium-doped sodium bismuth titanate

Na1/2Bi1/2TiO3 (NBT) doped with BaTiO3 (BT) has recently shown promising pi ezoelectric properties in single crystal form. The piezoelectric properties appear to be highly dependent on BT concentration, with compositions close to the morphotropic phase boundary (similar to 6% BT) having the highest p iezoelectric coefficients. Previous studies have resulted in conflicting co nclusions regarding the presence and nature of the superlattice in NET. Usi ng HREM and hot-stage TEM electron diffraction, we show that flux-grown sin gle crystals of compositions (1 - x)NBT-xBT with x < 0.08 exhibit superlatt ice reflections that are present from room temperature up to 500 degrees C, above which temperature they reversibly vanish. The reflections are consis tent with a superstructure due to single-axis in-phase octahedral tilt (a(0 )a(0)c(+)). The dependence of the superlattice reflection intensity on temp erature and BT content as well as possible mechanisms of superlattice forma tion are discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.