LOW-LOSS SINTERED DIELECTRIC RESONATORS WITH HTS THICK-FILMS

The combination of high-Q dielectric resonators and high-temperature s uperconducting (HTS) films offer many advantages in the area of cellul ar and satellite communications. The high cost of single crystal diele ctrics and HTS thin films may be unattractive in certain applications. Superconducting thick films and polycrystalline ceramic dielectrics o ffer a high performance, low-cost alternative to high-Q thin film/sing le crystal dielectric resonators. The loss of polycrystalline ceramics of Al2O3, Ba(Mg1/3Ta2/3)O-3 (BMT), and Zr0.875Sn0.25Ti0.875O4 (ZTS) h as been studied. Alumina, Al2O3,has been studied as a model material f or dielectric loss. Theory predicts that the loss in single crystal sa pphire should follow a T-5 dependence. However, at low temperatures th e loss is dominated by extrinsic losses due to crystal imperfection, r esidual dopant atoms, dislocations, and other lattice defects and the T-5 dependence does not hold. In polycrystalline alumina the intrinsic loss is immediately masked by these extrinsic losses, even at room te mperature, and a simple T dependence is observed. Results on polycryst alline alumina show that Q's well in excess of 10(5) at 10 GHz and 77 K can be achieved in a design made compact by the use of a HTS thick f ilm shield.