Multiple layer structures and superconductivity

Multiple perovskite structures of the general formula [[A,A′][B,B′]O] and related materials containing several perovskite layers such as the thallium oxide superconductors TlACaCuO are important classes of materials as regards superconductivity. The former stretch from n=2 for BaInCuO through YBaCuO, GdBaTiCuO and GdBaCaCuTiO to SrCuO with n = 3, 4, 5, ∞ respectively; the later includes phases such as TlSrCuO and TlBaCaCuO. The syntheses, structures and characterisation of a number of new materials from these classes, with high and low n, are described and their electronic properties discussed in terms of their structural features.