STRUCTURAL RELATION BETWEEN SUPERCONDUCTING OXIDES, AURIVILLIUS PHASES ANDRUDDLESDEN-POPPER PHASES

Abstract

The Ruddlesden-Popper phases can be described as a stacking of v or v′ CaTiO 3 and w or w′ MO structural units with bcc M lattice and O at octahedral interstices. 50% of all octahedral interstices in the bcc M lattice are occupied in CaTiO 3, 33% in MO. The Aurivillius phases can be derived as complementary structures with an occupation of the 67% vacant sites of MO leading to MO 2 units similar to the CaF 2 structure. 14 different structures are obtained as combinations of up to 8 v and w units. The structures can also be described by the sequence of coordination numbers of metal atoms with respect to oxygen. The superconducting phases known so far are with different donor elements: e + for Ruddlesden-Popper phases and e – for Aurivillius phases.