A new mixed phase ceramic superconductor based on the Y-Ba-Cu-O system with addition of tellurium

We fabricated a new type of superconducting ceramic satisfying the stoichiometric ratio of YTexBa4Cu6Oy with x ranging from 0 to 0.8, using compounds CuTeO3, Y2O3, BaCO3 and CuO. The Tc (R = 0) values of these superconductors are found to fall in the 89–94 K range. When x = 0.72, the critical current density Jc is found to be enhanced about 7 times compared to that of the YBa4Cu6Oy (or the common YBa2Cu3O7−δ) ceramic. The lower and upper limits of Jc measured and estimated for the best sample reach values of 1250 Acm−2 and over 104Acm−2, respectively. X-ray and SEM analyses indicate clearly that these new superconductors have crystal structures very much different from that of the well-known Y-123 specimen. In particular, we found that the nominal YBa4Cu6Oy ceramic is made up of a dominant structure YBa4Cu5O11−δ plus a small amount of the common 123 phase. The crystal lattice constants of this 145 new phase are roughly estimated to be: a = 5.240 Å, b = 5.827 Å, c = 11.507 Å. When Tc, is mixed in, the mechanical hardness of the resulting ceramic is much enhanced.