Microwave dielectric ceramics in the system (MgCa)TiO3-MgAl2O4

Ceramics in the Al2O3-CaTiO3-MgTiO3 system have been investigated with respect to their phases, sintered density and dielectric properties. In addition to MgTiO3, CaTiO3 and MgAl2O4 phases, some minor phases are also found to be present in the sintered samples. For most compositions, sintered densities in the range of 90 to 95 % are obtained. The dielectric constant decreases with increasing MgAl2O4 content nearly in agreement with the logarithmic rule. The value of Q.f reaches 33,000. The temperature coefficient of frequency (TCF) is negative and its magnitude increases first slowly and then rapidly as the MgAl2O4 content increases. Further adjustment of composition and processing leads to near zero TCF, high Q.f and low dielectric constant.