The reciprocal lattice and defect structure of the crystallographic shear (CS) structures in perovskite-based "Pb2Fe2O5" are investigated using transmission electron microscopy. The reciprocal space for all observed 1/2(h0l)p CS structures can be described with the same average pseudocubic unit cell with a ≈ ap (ap - the parameter of the perovskite subcell), and modulation vector q ≈ αa* + γc* with α/γ ≈ h/l and superspace group X2/m(α0γ) with a centering vector [1/2,1/2,1/2,1/2]. The defect structure is characterized by numerous mirror twins and coherent intergrowths of 1/2(h0l)p CS structures with different (h0l)p. There are no single CS planes in the perovskite matrix and there is no variation of the perovskite block thickness between the successive CS planes. The crystallographic similarity and the structural and chemical differences between the CS structures in "Pb2Fe2O5" and those in ReO3 and/or TiO2-type oxides are discussed.
|Number of pages||8|
|Journal||Solid State Sciences|
|Publication status||Published - Apr 2008|