MULTIPLE LAYER STRUCTURES AND SUPERCONDUCTIVITY

Multiple perovskite structures of the general formula [[A,A'][B,B']O3- x](n) and related materials containing several perovskite layers such as the thallium oxide superconductors TlA(2)Ca(n-1)Cu(n)O(4+2n) are im portant classes of materials as regards superconductivity. The former stretch from n=2 for Ba2InCuO4+delta through YBa2Cu3O7, Gd2Ba2Ti2Cu2O1 1 and Gd2Ba2CaCu2Ti3O14 to SrCuO2 with n = 3, 4, 5, infinity respectiv ely; the later includes phases such as TlSr2CuO4.5 and TlBa2Ca4Cu5O13. The syntheses, structures and characterisation of a number of new mat erials from these classes, with high and low n, are described and thei r electronic properties discussed in terms of their structural feature s.