ABSTRACT
Depending on the coordination of B-site cations, the shape of the BO6 octahedra in an ideal cubic perovskite can transform into cubic, tetrahedral, pyramidal, planar, or linear arrangements, ultimately resulting in crystal structures with lower symmetries than that of a cubic perovskite. In general, layered perovskites are composed of A-site cationic layers that separate the BO6 octahedral slabs, forming 2D slabs of ideal perovskite structures separated by 2D A-site cation layers. The layered perovskite-structured superconductors with ACuO3 perovskite slabs are replacing conventional metallic alloys due to their high superconducting temperatures. The superconductivity of such materials is originated from the CuO2 sheets present in them. A perovskite structure is said to be anion deficient when the sum of the charges of the A and B cations in the oxide perovskites is below six, which is equal to six for ideal perovskites.
