US Patent 7754634 Low-loss microwave dielectric ceramic

There is provided a low-loss microwave dielectric ceramic having a composition represented by xCaO.yLn2O3.zAl2O3.mTiO2 wherein Ln is Nd or Sm, 25.0 mole %≦x≦75.0 mole %, 10.0 mole %≦y≦30.0 mole %, 10.0 mole %≦z≦30.0 mole %, 0.8 mole %≦m≦20.0 mole %, x+y+z+m=100 mole %. It has a dielectric constant in the range from 18 to 25, an extremely large Qf value ranging from 80,000 to 200,000 GHz, and a temperature coefficient of resonant frequency tunable in the vicinity of 0. It can make the applications of dielectric resonators, filters, and antennas extended to higher frequency and larger power; it can also be applied to microwave capacitors, temperature-compensated capacitors, microwave substrates, et al.