CHARACTERIZATION OF YBA2CU3O7-X LAYERS PREPARED BY ELECTROPHORETIC DEPOSITION

YBa2Cu3O7-x-layers prepared by electrophoretic deposition in nonaqueous media have been characterized with special attention to the influence of the substrate metal on the superconducting characteristics. Interfacial reactions between the core metal and the coated YBa2Cu3O7-x during the sintering process play a decisive role for the superconducting properties. Au and Ag are found to be the best substrates, which brings an onset temperature at about 91 K and zero resistance state at about 85 K. On the other hand, Pt, Ni-Cr (Nichrome), Cr-Al-Co (Kanthal), and Ni-Mo-Fe-Mn (Hastelloy) are ruled out because of interfacial reactions. The use of Ni had some difficulties, but its performances can still be improved, if the surface is slightly oxidized or coated with Ag before being used as the electrode. The rejected metals are, more or less, responsible for catalyzing the formation of nonsuperconducting Y2BaCuO5. These metals can, however, be passivated by coating with a thin barrier layer of Ag or Ni/Ag, and the zero resistance is then achieved, for example, at about 76 K in Pt/Ni-Ag.