Microwave dielectric properties of temperature-stable (Mg0.95Co0.05)2TiO4–Li2TiO3 composite ceramics for LTCC applications

In this paper, the effects of Li2O–B2O3–Bi2O3–SiO2 (LBBS) glass on the phase formation, sintering characteristic, the microstructure and microwave dielectric properties of temperature-stable (Mg0.95Co0.05)2TiO4–Li2TiO3 ceramics were investigated. (Mg0.95Co0.05)2TiO4–Li2TiO3 powders were obtained by using the traditional solid-state process. A small amount of LBBS doping can effectively reduce sintering temperature and promote the densification of the ceramics. X-ray diffraction analysis revealed not only the primary phase (Mg·Co)2TiO4 associated with Li2TiO3 minor phase but also a third phase (Mg·Co)TiO3. The dielectric constant and Qf values vary with the doping amount of LBBS and sintering temperatures. With the compensation of the positive temperature coefficient (τf) of Li2TiO3 and the negative τf of (Mg0.95Co0.05)2TiO4, the τf of the specimens fluctuates around zero. The (Mg0.95Co0.05)2TiO4 ceramic with 2.5 wt% LBBS addition and sintering at 900 °C for 4 h exhibited excellent microwave dielectric properties: ɛr = 19.076, Qf = 126100 GHz, and τf = 0.98 ppm/°C.