Performance of YBCO thick films in high-Q structures

Over the past 10 years a wide variety of different resonant structures have been fabricated from High Temperature Superconductor (HTS) materials for an extensive range of possible RF and microwave applications. The near term applications are those that make use of passive components such as high Q resonators for low phase noise oscillators and high performance filters for satellite or communications purposes. Although there are several different HTS materials, such as YBCO, BSCCO and TBBCO, each particular material can be subdivided according to their means of production and, for microwave applications, there are essentially two types. The first is thin film material which is an epitaxial film, usually <1 micron thick and grown by techniques such as Molecular Beam Epitaxy (MBE) or laser ablation on a single crystal substrate such as MgO or LaAlO₃. The second is thick film material 50-100 microns in thickness which is polycrystalline and is deposited in the form of a viscous ink upon a polycrystalline substrate. This paper is concerned with thick film YBCO films on zirconia substrates fabricated either by doctor blading or screen printing techniques. One advantage of the thick film approach is that films can be deposited onto large areas and curved to form three dimensional structures which are impossible to construct using thin film deposition techniques. A range of very high Q resonant structures have been realized and these are compared and contrasted in the paper