LAUSR

Abstract Microwave dielectric properties of Li 2 Mg 3− x Ca x TiO 6 (x=0–0.18) ceramics were studied using a conventional solid-state route to find temperature stable and high Q microwave ceramics. As the calcination temperature was 500 °C, the Li 2 TiO 3 phase with monoclinic rock salt structure in C 2 /c space group started to form. When the samples were calcined from 600 °C to 900 °C, the XRD patterns exhibited a remarkable chemical reaction between the MgO and Li 2 TiO 3 phases, which eventually formed the Li 2 Mg 3 TiO 6 phase. The results indicated the Li 2 Mg 3 TiO 6 and CaTiO 3 co-existed with each other and formed a stable composite system when the calcium content was added. The SEM photographs indicated that the pores caused by the Li evaporation could be effectively reduced due to the appearance of CaTiO 3 . As x was increased from 0 to 0.18, the relative density was significantly improved due to the elimination of pores. As the Ca content increased, the dielectric constant (er) increased from 14.8 to 20.6; the quality factor (Q×f) decreased from 148,713 GHz to 79,845 GHz, and the temperature coefficient of resonant frequency (τf) significantly increased from −42.4 to +10.8 ppm/°C due to the increased amount of CaTiO 3 . Therefore, at x=0.12, the LMC x T ceramics sintered at 1280 °C for 6 h displayed excellent comprehensive properties of er=17.8, Q×f =102,246 GHz and τf=−0.7 ppm/°C.