  The oxygen octahedral tilted domains in
0.90(Bi1/2Na1/2)TiO3-0.5(Bi1/2K1/2)TiO3-0.5BaTiO3 lead-free perovskite
piezoelectric ceramic have been studied by transmission electron microscopy
(TEM). Selected-area electron diffraction patterns shows the 1/2ooo and 1/2ooe
reflections, indicating the presence of antiphase (a-a-a-) and in-phase
(aoaoc+) octahedral tilting, respectively. The morphology and distributions of
these tilted domains are shown in the centered dark-field images. Further, the
Bragg-filtered high-resolution TEM image reveals that the size of the in-phase
tilted domains varies from 1 to 8 nm across. The ceramic contains the mixture
of non-tilted and variants of the antiphase and in-phase tilted domains.
