Doped Ca(Ca1/4A2/4Ti1/4)O3 (A=Nb, Ta) Dielectrics for Microwave Telecommunication Applications

Ca(Ca_1/4A_2/4Ti_1/4)O₃ (A=Nb, Ta) dielectric resonator materials have been prepared by the solid-state ceramic route. The effects of various amounts of di-, tri-, tetra-, penta-, and hexavalent impurities on the structure, microstructure, density, and microwave dielectric properties of the complex perovskites have been investigated. The structure of the parent materials remained unchanged while slight increase in density was observed with a small amount of certain dopants. An improvement in dielectric constant, quality factor, and temperature coefficient of resonant frequency was observed with the doping of small amounts of MgO, ZnO, NiO, CuO, Co₃O₄, Cr₂O₃, SnO₂, and Sb₂O₅. A correlation between the microwave dielectric properties of Ca(Ca_1/4A_2/4Ti_1/4)O₃ (A=Nb, Ta) ceramics and ionic radius of the dopant has been observed. The reported ceramics are potential candidates for dielectric resonator applications in wireless communication devices operating in the S and C bands.