Stabilities of all three superconducting phases in the Bi-Sr-Ca-Cu-O system under high oxygen pressure were investigated over a wide range of temperatures. Only the 2201 phase is stable under high oxygen pressure; the 2212 and 2223 phases transform to a new orthorhombic perovskite-related phase of the GdFeO3 type. Its average composition is (Sr,Ca)0.75(Bi,Cu)1.00O3-δ with lattice parameters a=6.0082(7), b=8.3768(14) and c=5.8631(8) A ̊. This new phase is non-superconducting but readily reconverts to a superconducting 2212 phase when re-annealed in air.
- Bi-Sr-Ca-Cu-O superconductors
- high pressure