2001 Volume 42 Issue 9 Pages 1890-1892
A new superconducting cuprate (Sr0.7Ca0.3)3Cu2O5+δ has been synthesized under high pressure. CaO2 has been used to make a homogeneous oxidizing atmosphere. X-ray diffraction measurements on the bulk sample revealed that (Sr0.7Ca0.3)3Cu2O5 (325-type) phase was found in the top surface of the columnar sample, (Sr0.7Ca0.3)4Cu3O7 (437-type) phase in the bottom surface and 325-type+437-type mixed phase in a cross section parallel to the column axis. Segregations of 325-phase and 437-phase were supposed to take place in the upper and lower parts of the sample, respectively. Nearly single phase samples of 325-type and 437-type crystal were gained by grinding from the upper part and the lower part of the sample, respectively, using abrasive papers. Magnetic susceptibility measured by SQUID and electrical resistivity measurements showed that superconductive transition temperatures are 106 K in the 325-phase and 110 K in the 437-phase.