THE LEAST ANISOTROPIC HIGH-TC SUPERCONDUCTOR CUBA2CA3CU4O12-Y (CU-1234)

A nontoxic high-Tc (=118 K) superconductor CuBa2Ca3Cu4O12-y (Cu-1234) has a low superconducting anisotropy (gamma = 1.5) and a long coherenc e length along c-axis (xi(c) = 10 Angstrom). The superconducting aniso tropy of Cu-1234 was compared with other cuprate superconductors by us ing the experimental data from a common measurement method of anisotro py. The Cu-1234 was found to have the least superconducting anisotropy among cuprate superconductors. The least anisotropy originates from a strong superconducting-coupling between superconducting Ca3Cu4O8-bloc k layers mediated by superconductive charge-reservoir CuBa2O4-y layer, the thickness of the superconducting block layer (9.6 Angstrom) and h igh carrier concentration.