High oxygen pressure synthesis of new copper oxide superconductors

The unique coordination of the copper ions in +1, +2, and +3 oxidation states, which are stable in a range of oxygen partial pressure. 10−6 1 atm. These materials, La2CuO4+δ, La2−xCa x CuO4, and YSr2−xLa x Cu3O7+δ, offer a unique opportunity to study the relationship between superconductivity and structural, magnetic, and chemical properties.