Low temperature sintering and microwave dielectric properties of Li2TiO3–Li2WO4 composite ceramics

(1−x)Li2TiO3–xLi2WO4 composite ceramics could be densified at low temperature (950 °C) by liquid-phase sintering. The phase assemblage, microstructure and chemical compatibility with Ag were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Microwave dielectric properties were measured with a network analyzer. It was found that Li2TiO3 and Li2WO4 coexisted after sintering at 950 °C/2 h. Both εr and τf of the composite ceramics decreased linearly with the increase of Li2WO4 phase. The optimized Qf value increased with increasing Li2WO4 content and reached a maximum value of about 80,000 GHz at x=0.1–0.15. Further increase in x remarkably decreased the Qf value. The 0.15 composition sintered at 950 °C possesses excellent combined microwave properties with εr=18.1, Qf=81,099 GHz and τf=2.2 ppm/°C. It indicates that Ag diffused into the Li2WO4 phase and formed (Li,Ag)2WO4 solid solution at 900 °C/2 h, although isolated Ag still existed in the cofired specimen.