Octahedral tilting domain boundary in calcium-modified lead titanate ceramics

Characteristics of atomic ordering and TiO6 octahedron tilting boundaries of Pb1-xCaxTiO3 (x.0.5) were studied using electron diffraction and transmission electron microscopy in the present work. Pb0.5Ca0.5TiO3 specimens exhibit 1/2(100), 1/2(110) and 1/2(111) extra reflections regularly in electron diffraction patterns. However, chemical ordering behavior may not be able to explain absence of some diffraction sports. Dark field images show types of different image characteristics using extra reflections of 1/2(111) as well as 1/2(100) and 1/2(110), implying different origins of the super-reflections. An octahedron-tilting scheme was considered to interpret diffraction behavior and wavy boundaries in Pb1-xCaxTiO3 materials. Contrast characterstics of microstructural features and adjacent matrix indicate that the wavy lines are attributed to the boundaries of octahedron-tilting domains.