THE PROPERTIES OF Y1BA2CU3O7-DELTA THIN-FILMS WITH SILVER DOPING PREPARED BY SPRAY PYROLYSIS

Superconducting, silver-doped films of Y1Ba2Cu 3O7-δ have been deposited by spray pyrolysis of aqueous nitrate solutions onto MgO substrates. The superconducting transport properties, microstructure, and microwave losses have been characterized for various amounts of AgNO3 added to the spraying solution. These films had resistive transition temperatures between 79 and 85 K with widths from 3 to 7 K. The room-temperature resistivity was a strong function of the silver doping, dropping by a factor of 50 for the heavily doped films. Critical current densities at 4 K were typically several 103 A/cm2 with little correlation to the silver doping. Lattice constants also were not significantly affected by the silver doping level, however, lightly doped films were denser, had the strongest c axis preferred orientation, and a smoother surface. Rf surface resistance was measured at 18 GHz, and for the best films dropped a factor of 10 below copper by 40 K. The London penetration depth was estimated to be approximately 1 μm for the best films.