Abstract
Microstructural studies on (1 −x)Ba(Mg1/3Nb2/3)O3–xCa(Mg1/3Nb2/3)O3 (BCMN) complex perovskite compounds, which are mixtures of Ba(Mg1/3Nb2/3)O3 (BMN) and Ca(Mg1/3Nb2/3)O3 (CMN), were conducted using scanning electron microscopy, transmission electron microscopy, and X‐ray diffractometry. Pure BMN and CMN both have a 1:2 ordered structure, via the chemical ordering of B‐site cations; however, the tilting of oxygen octahedra is involved in pure CMN, whose structure has a 1:2 ordered monoclinic unit cell that is characterized by (±1/6,±1/6,±1/6)‐type superlattice reflections in electron diffraction patterns along the [110] zone axis that is based on a simple cubic perovskite. Studies of the morphologic differences have indicated two types of inhomogeneities in a mixture of the BCMN system: (i) a rather large‐scale segregation (i.e., grain sizes of several micrometers), where the grains are separated compositionally as being barium‐rich or calcium‐rich, and (ii) fine‐scale lamellar‐type segregations 20 nm wide and 200 nm long. The segregation that is caused by Ba and Ca ions can be identified by the difference of superlattice modulations from high‐resolution transmission electron microscopy lattice images.
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