MICROWAVE DIELECTRIC-PROPERTIES OF MAGNESIUM CALCIUM TITANATE CERAMICS PREPARED BY SEMI-ALKOXIDE METHODS

(Mg0.95Ca0.05)TiO3 powders were synthesized by two semi-alkoxide metho ds employing titanium isopropoxide and acetates, nitrates of magnesium and calcium. These powders without milling were fired in the temperat ure range of 1250 to 1500 degrees C. The sintered dense ceramics, with two phases (MgTiO3 and CaTiO3), showed a much higher microwave dielec tric quality factor compared to that prepared through a conventional m ixed oxide method (Q = 7000 at 10.3 GHz). It was shown that the morpho logy of prepared powders plays an important role on the relative densi ty 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 gra in size. It was suggested the second phase and its distribution in the matrix of MgTiO3 result in the Q deviation. The rapid grain growth ca uses a partial accommodation of second phase into grain. The samples w ith such accommodation revealed a higher reduction in microwave Q-fact or than that the samples with accommodation of CaTiO3 on the grain bou ndary.