Microwave dielectric properties of magnesium calcium titanate ceramics prepared by semi-alkoxide methods

(Mg0.95Ca0.05)TiO3 powders were synthesized by two semi-alkoxide methods employing titanium isopropoxide and acetates, nitrates of magnesium and calcium. These powders without milling were fired in the temperature range of 1250 to 1500 degrees C. The sintered dense ceramics, with two phases (MgTiO3 and CaTiO3), showed a much higher microwave dielectric quality factor compared to that prepared through a conventional mixed oxide method (Q = 7000 at 10.3 GHz). It was shown that the morphology of prepared powders plays an important role on the relative density and the grain size of MgTiO3. Dielectric constant was affected not by the grain size and oxygen deficiency but by the relative densities. Q was not affected by the relative density, oxygen deficiency and grain size. It was suggested the second phase and its distribution in the matrix of MgTiO3 result in the Q deviation. The rapid grain growth causes a partial accommodation of second phase into grain. The samples with such accommodation revealed a higher reduction in microwave Q-factor than that the samples with accommodation of CaTiO3 on the grain boundary.