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The microstructure of lead-free 0.94(Na0.5Bi0.5)TiO3-0.06BaTiO3 (BNBT-6)piezoelectric ceramics was investigated by different analysis techniques.X-ray diffraction (XRD)result reveals the coexistence of rhombohedral and tetragonal symmetry in the structure of BNBT-6 ceramics at room temperature.Selected area electron diffraction (SAED) patterns reveal the presence of ordered domains in BNBT-6 ceramics.The superlattice reflections { h+1/2 k +1/2 0}and {h+1/2k+1/2l+1/2} of ordered domains mainly come from the octahedral tilt and chemical ordering of A-site atoms.High-resolution transmission electron microscopy (HRTEM) combined with image processing is an effective method to investigate the defects and the size of ordered domains in BNBT-6 ceramics.One-dimensional fringe images of superlattice reflections indicate that there are significant local Na and Bi atomic layer displacements and anti-phase boundaries as a results of chemical ordering,which provide a driving force for order-disorder transformation.A filtered HRTEM black/white image shows the size of ordered domains to be about 5-10 nm.