STRUCTURAL RELATION BETWEEN SUPERCONDUCTING OXIDES, AURIVILLIUS PHASES AND RUDDLESDEN-POPPER PHASES

The Ruddlesden-Popper phases can be described as a stacking of v or v' CaTiO3 and w or w' MO structural units with bcc M lattice and O at oc tahedral interstices. 50% of all octahedral interstices in the bcc M l attice are occupied in CaTiO3, 33% in MO. The Aurivillius phases can b e derived as complementary structures with an occupation of the 67% va cant sites of MO leading to MO2 units similar to the CaF2 structure. 1 4 different structures are obtained as combinations of up to 8 v and w units. The structures can also be described by the sequence of coordi nation numbers of metal atoms with respect to oxygen. The superconduct ing phases known so far are with different donor elements: e+ for Rudd lesden-Popper phases and e- for Aurivillius phases.