STRUCTURAL RELATIONSHIPS BETWEEN COMPOUNDS BASED ON THE STACKING OF MIXED LAYERS RELATED TO HEXAGONAL PEROVSKITE-TYPE STRUCTURES

Ever since the discovery of high-temperature superconductivity in laye red copper oxides, interest in materials exhibiting two-dimensional cr ystal structures related to perovskites (AMX(3)) has greatly increased , This review deals with crystal structures of various phases derived from perovskite with mixed stacking of [AX(3)] and [A(n)X(m)] (n + m l ess than or equal to 4) layers. Based on their structural relationship s with the perovskite-related hexagonal polytypes, the possibility of forming compounds adopting new structure types derived from mixed stac king of various layers will be discussed. In addition, this review wil l also highlight the similarities between the perovskite structure and the structures of phases as varied as vanadates, phosphates etc., in which part of the structure is made up of cations present in a tetrahe dral environment.