Superstructures Based on Oxygen Ordering

In some oxides, formation of superstructures is merely due to oxygen ordering. A good example was demonstrated by Reller and coworkers in 1984, by showing many distinct superstructures in perovskite-type oxides CaMn03, t with oxygen contents of 2.5, 2.556, 2.667, 2.75 and 2.80 [38]. 

An incommensurate superstructure is a superstructure derived from a basic structure without a proportional relation of dimensions to the basic unit cell. This type of superstructure is often found in mixed oxides. A good example is Bi203-based solid solutions. 

Some incommensurate superstructures are developed from lattice distortion instead of partial ordering of cations. One example is the superconducting oxide Bi2+)tSr2Cai jtCu20g, 6 [43, 44]. 

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