Microwave Surface Resistance of Bi$_{\bf 2}$Sr$_{\bf 2}$CaCu$_{\bf 2}$O x Thick Films on Large-Area Metallic Substrates

As a feasibility study for application of a high-T-c material to an accelerator cavity, Bi2Sr2CaCu2Ox thick films were formed on large-area metallic substrates. The microwave surface resistance of the films was measured over a temperature range from 4.2 K to 300 K using a demountable cylindrical copper cavity operated at 3 GHz in the TE011 mode. The area of the end plate was 177 cm(2) and the thickness of the films was around 50 mu m. The films were formed either on silver foils (on copper) or on a silver plate, coated by either a screen-printing or a spray-coating method, sintered either in air or in a Bi2O3 atmosphere, both at 885-890 degrees C, and either annealed in nitrogen gas at 600 degrees C or not annealed. The ratio of the microwave surface resistance of the best film to that of the copper was 0.18 at 10 K and 0.05 at 77.3 K. A comparison of the microwave surface resistance is made between Bi2Sr2CaCu2Ox and YBa2Cu3O7-x films.