Structural evolution and microwave dielectric properties of MgO–LiF co-doped Li2TiO3 ceramics for LTCC applications

In this study, MgO–LiF co-doped Li2TiO3 ceramics were prepared by the conventional solid-state ceramic route. Continuous solid solutions between Li2TiO3, LiF and MgO were formed across the entire compositional range. With increasing MgO content, the degree of long range order decreased, and the crystalline structure transformed from monoclinic phase to cubic phase. The addition of LiF significantly promoted the sinterability of Li2TiO3 based ceramics and successfully reduced the sintering temperature. The Qf and τf values could be further optimized by doping MgO. Well-densified structure with excellent microwave dielectric properties of εr=23.21, Qf=131,668 GHz, and τf=−0.46 ppm/°C was obtained for 0.87Li2TiO3–0.05MgO–0.08LiF ceramics sintered at 950 °C. In addition, Li2TiO3–MgO–LiF ceramics were compatible with Ag electrodes, making them suitable for low-temperature co-fired ceramic (LTCC) applications.