Superconductivity at High Temperatures in Bismuth and Copper Based Oxides

High temperature superconductivity in layered copper oxides has now been known for more than two years. New materials are constantly being discovered which shed new light on both the chemistry and the physics of high T sub c. I will describe in detail our work on a new family of layered copper oxide superconductors based on hole doping of Pb sub 2 Sr sub 2 LnCu sub 3 O sub 8+-delta by partial substitution of alkaline earth ions for the lanthanide. Although they have the planes of CuO sub 5 square pyramids characteristics of the other copper-oxide superconductors, the new compounds belong to a distinct structural series, with wide scope for elemental substitution. There is an unusual combination of reduced lead and copper cations with oxidized copper cations in the structure which gives insight into the role of internal charge distribution in controlling superconductivity.