High Q-value resonators for the SHF-region based on TBCCO-films

We used a sapphire dielectric resonator with a copper cylindrical shield and two endplates replaced by HTS layers for very accurate surface resistance measurements of TBCCO films made by the two step method. This technique allows for the preparation of high quality 2-in diameter Tl-2223 superconducting films with surface resistance values (R/sub s/) smaller than 100 /spl mu//spl Omega/ at 5.6 GHz and 77 K. The use of these films in sapphire dielectric resonators yields resonators for the C-band with very high unloaded quality factors (Q/sub o/>2/spl times/10/sup 6/ at 77 K). Such high Q/sub o/-values are not reached with any conventional resonators of comparable size.