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

Abstract We fabricated a new type of superconducting ceramic satisfying the stoichiometric ratio of YTe x Ba 4 Cu 6 O y with x ranging from 0 to 0.8, using compounds CuTeO 3 , Y 2 O 3 , BaCO 3 and CuO. The T c ( R = 0) values of these superconductors are found to fall in the 89–94 K range. When x = 0.72, the critical current density J c is found to be enhanced about 7 times compared to that of the YBa 4 Cu 6 O y (or the common YBa 2 Cu 3 O 7−δ ) ceramic. The lower and upper limits of J c measured and estimated for the best sample reach values of 1250 Acm −2 and over 10 4 Acm −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 YBa 4 Cu 6 O y ceramic is made up of a dominant structure YBa 4 Cu 5 O 11−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 A , b = 5.827 A , c = 11.507 A . When T c , is mixed in, the mechanical hardness of the resulting ceramic is much enhanced.