Low-temperature sintering and microwave dielectric properties of Ca(Li1/3Ta2/3)O3−δ–CaTiO3 ceramics

New Ca[(Li1/3Ta2/3)1−xTix]O3−δ (0.5⩾x ⩾0) solid solutions with the addition of B2O3 were prepared by a conventional oxide mixture method to develop a microwave resonator with a low sintering temperature. It was shown that Ca(Li1/3Ta2/3)O3−δ ceramics did not occur as a single phase but rather as a mixture of a perovskite-type phase with a minor amount of Li3TaO4. The perovskite phase exhibited 1:2 ordering of Li and Ta on the B-sites. The substitution of Ti4+ for Li1+ and Ta5+ stabilized the perovskite phase, destabilized 1:2 ordering, and improved the grain growth of Ca[(Li1/3Ta2/3)1−xTix]O3−δ (x=0.2, 0.3) ceramics. As the x composition increased from 0 to 0.5, the dielectric constant, ε, increased from 24 to 48, the quality factor, Q×f, decreased from 42,000 to 11,000 GHz, and the temperature coefficient of resonator frequency, τf, increased from a negative value to a positive one. A new microwave dielectric material with ε=35, Q×f =22,800 GHz, and τf=−4.1 ppm/°C was obtained in the Ca[(Li1/3Ta2/3)0.7Ti0.3]O3−δ ceramics doped with B2O3 sintered at a temperature as low as 1050 °C.