(1) Superconductivity Research Laboratory-ISTEC, 1-10-13 Shinonome, Koto-ku, 135 Tokyo, Japan;(2) Institute for Solid State Physics, University of Tokyo, 7-22-1 Roppongi, Minato-ku, 106 Tokyo, Japan
Abstract:
It is shown for (Sr, Ca)1–yCuO2.00+z (nominal composition) superconductors fabricated under a high pressure of 5 GPa and at 930°C that, as z increases, the Meissner fraction increases from a few percent to 20% and then starts to decrease. In the X-ray powder diffraction pattern for the sample with the maximum Meissner fraction, it is obvious that the infinite-layer structure has been decomposed and a new structure becomes the major phase. It appears that the new structure is the 0223 structure which consists of rock-salt and the infinite-layer type blocks. This material is likely to be a new superconducting cuprate.