New experimental results for microwave conductivity of high-T/sub c/ superconductors and consequences for applications to linear devices

Experimental results on the surface impedance of the oxide superconductor YBa/sub 2/Cu/sub 3/O/sub 7/ in the frequency range from 3 to 90 GHz and the temperature range from 4.2 to 300 K are presented for single-crystal and polycrystalline layers. The best results were achieved with a film grown epitaxially on SrTiO/sub 3/ by pulsed laser ablation, leading to a surface resistance of less than 8 m Omega at 86.7 GHz and 77 K. Thus, applications to microwave and millimeter-wave components which require a much higher quality factor than realizable with normal conductors or which have to be miniaturized by some orders of magnitude can be envisaged. It may be possible to realize inductive films with electronically tunable properties.<>