High temperature superconducting microstrip resonators for the measurement of films made by pyrolysis

Microwave surface impedance measurements are reported for textured granular YBCO films made by a novel spray pyrolysis method on the surface of a YSZ substrate. A parallel plate resonator was formed by placing the film and substrate on top of a copper ground plane. Microwave measurements were made at nitrogen temperatures on the fundamental mode at ~4.7 GHz. A model has been developed to extract the penetration depth and impedance of the finite thickness granular film. We obtain values for penetration depth λ_g~3.6 μm and, using independent measurements of the critical current and grain size, a surface resistance R_g~13 mΩ