Published online by Cambridge University Press: 31 January 2011
Thin-film GdBa2Cu3Ox superconductors with an onset Tc > 90 K have been produced. The films were fabricated by thermal reaction in an oxidizing atmosphere of electron-beam deposited Ba/Gd/Cu multilayers. Attempts to produce the superconducting phase YBa2Cu3Ox by multilayer reaction were unsuccessful due to a positive heat of mixing between Y and Ba. The appearance of a wide superconducting transition in GdBa2Cu3Ox films may be the result of tunneling through a nonsuperconducting second phase.