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.