  Samarium substituted bismuth ferrite (BiFeO3) ceramics prepared by sol-gel
synthesis method were studied using both local scale and microscopic
measurement techniques in order to clarify an evolution of the crystal
structure of the compounds across the morphotropic phase boundary region. X-ray
diffraction analysis, transmission and scanning electron microscopies, XPS,
EDS/EDX experiments and piezoresponse force microscopy were used to study the
structural transitions from the polar active rhombohedral phase to the
anti-polar orthorhombic phase and then to the non-polar orthorhombic phase,
observed in the Bi1-xSmxFeO3 compounds within the concentration range of 0.08 <
x < 0.2. The results obtained by microscopic techniques testify that the
compounds in the range of 0.12 < x < 0.15 are characterized by two phase
structural state formed by a coexistence of the rhombohedral and the anti-polar
orthorhombic phases; two phase structural state observed in the compounds with
0.15 < x < 0.18 is associated with a coexistence of the anti-polar orthorhombic
and the non-polar orthorhombic phases. Local scale measurements have revealed a
notable difference in the concentration range ascribed to the morphotropic
phase boundary estimated by microscopic measurements, the obtained results
testify a wider concentration range ascribed to a coexistence of different
structural phases, the background of the mentioned difference is discussed.
