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

Abstract

New Ca[(Li 1/3 Ta 2/3 ) 1-x Ti x ]O 3-δ (0.5≥x≥0) solid solutions with the addition of B 2 O 3 were prepared by a conventional oxide mixture method to develop a microwave resonator with a low sintering temperature. It was shown that Ca(La 1/3 Ta 2/3 )O 3-δ ceramics did not occur as a single phase but rather as a mixture of a perovskite-type phase with a minor amount of Li 3 TaO 4 . The perovskite phase exhibited 1:2 ordering of Li and Ta on the B-sites. The substitution of Ti 4+ for Li 1+ and Ta 5+ stabilized the perovskite phase, destabilized 1:2 ordering, and improved the grain growth of Ca[(Li 1.3 Ta 2.3 ) 1-x Ti x ]O 3-δ (x=0.2, 0.3) ceramics. As the x composition increased from 0 to 0.5, the dielectric constant, e, 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, τ f , increased from a negative value to a positive one. A new microwave dielectric material with e=35, Q×f = 22,800 GHz, and τ f = -4.1 ppm/°C was obtained in the Ca[(Li 1.3 Ta 2.3 ) 0.7 Ti 0.3 ]O 3-δ ceramics doped with B 2 O 3 sintered at a temperature as low as 1050 C.