Investigations on the phase formations, properties and single crystal growth in the high-Tc superconducting Ca-Sr-Bi-Cu-O system

We have performed investigations on the Ca-Sr-Bi-Cu-O system with respect to high-Tc superconductivity and structural properties. It is shown that there are two high-Tc superconducting phases in the system, i.e. a 110 K and an 85 K phase. The 85 K phase has a body-centred tetragonal structure with a stoichiometry of CaSr2Bi2Cu2O8. The 110 K phase is closely related to the 85 K phase. It is formed only in a very narrow temperature range and easily deteriorates to the phase with the lower Tc by quenching. Although some samples show a large diamagnetic signal at 110 K in ac-susceptibility measurements, there is still evidence of the presence of the 85 K phase. X-ray diffraction studies, especially in the low-angle region, show a structural relation between these two superconducting phases. The procedures of the preparation and the characterization of the 85 K and 110 K polycrystalline superconducting phases as well as the single crystal growth of the 85 K superconducting phase are described

Equilibrium magnetization of a Bi2Sr2CaCu2Ox single crystal measured up to 20 T

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