10 GHz YBa2Cu3O7- deltasuperconducting ring resonators on NdGaO3substrates

YBa 2 Cu 3 O 7- delta thin films were formed on NdGaO 3 substrates by laser ablation. Critical temperatures greater than 89 K and critical current densities exceeding 2*10 6 A cm -2 at 77 K were obtained. The microwave performance of films patterned into microstrip ring resonators with gold ground planes was measured. An unloaded quality factor six times larger than of that of a gold resonator of identical geometry was achieved. The unloaded quality factor decreased below 70 K for both the superconducting and gold resonators due to increasing dielectric losses in the substrate. The temperature dependence of the loss tangent of NdGaO 3 was extracted from the measurements.