Microwave Properties of Bi2223 Thick Films on Ba(Sn, Mg, Ta)O3 Dielectric Disk

Abstract

We fabricated 2.1GHz TM010-mode microwave resonators with (Bi, Pb)2Sr2Ca2Cu3Ox (Bi2223) superconducting thick films on a Ba(Sn, Mg, Ta)O3 dielectric disk with a relative dielectric constant of er=24. The Bi2223 thick films were screen-printed on both sides of the dielectric disk and subjected to a double repetition of cold isostatic pressing at 0.4GPa and sintering at various temperatures ranging from 820 to 840°C. An increase of the sintering temperature raises the Bi2223 phase purity up to 98% on the surfaces of the thick films, but high-temperature sintering above 830°C causes a chemical reaction at the interface between the Bi2223 thick film and the dielectric disk. An optimization of the sintering temperature to 830°C gives the unloaded quality factors Qu as much as 74, 000 at 70K and 158, 000 at 25K, which correspond to surface resistances Rs of 0.34 and 0.15mΩ for Bi2223 thick films, respectively. These values are approximately 20 times higher than those for the resonator using Ag electrodes with the same structure.