NEW HIGH-T-C SUPERCONDUCTOR, (GEZCU1-Z)SR2CA2-XYXCU3OY ((GE,CU)-1223)PREPARED UNDER HIGH-PRESSURE

Phase search in the Ge-Sr-Ca/Y-Cu-O system under high-pressure of 6 GP a and 1300 degrees C was carried out. There exists a new superconducto r, (GezCu1-z)Sr2Ca2-xYxCu3Oy ((Ge,Cu)-1223) having the highest T-c of 90 K. X-ray and electron microscopic investigations showed that it has a M-1223-type structure (e.g. Tl-1223) with the Ge-Cu mixed atoms occ upying the M sites. Electron diffraction patterns of(Ge,Cu)-1223 gave a tetragonal lattice without any superlattice spots suggesting random arrangement between Ge and Cu in the (Ge,Cu) plane. Typical cell param eters were a = 3.8299(2), c = 14.582(1) Angstrom for a sample with a n ominal composition, (Ge0.4Cu0.6)Sr2Ca1.8Y0.2Cu3O9.3.