Ultra-low temperature fired glass-free Li2O–MO–WO3 (M = Co, Ni, Ca, Ba) microwave dielectric ceramics

The Li2O–MO–WO3 (M = Co, Ni, Ca, Ba) ceramics for ultra-low temperature co-fired ceramic application were prepared by using the conventional solid-state reaction route. The phase composition, microstructures, and microwave dielectric properties of the compounds were investigated systematically. The X-ray diffraction patterns show that the Li2O–MO–WO3 (M = Co, Ni) consist of CoWO4 (NiWO4), Li2WO4 and Li2W2O7 phases while Li2O–MO–WO3 (M = Ca, Ba) comprises CaWO4 (BaWO4) and Li2WO4 phases. The porosity and phase constitution acted as a controlling factor of dielectric constant in the Li2O–MO–WO3 (M = Co, Ni, Ca, Ba) ceramics. These compounds can be sintered at ultra-low temperature of 600–680 °C and exhibit good microwave dielectric properties with εr = 5.6–13.5, Q × f = 13,000–25,000 GHz, and τf =− 97.3 to − 38.3 ppm/°C, which made the compounds promising for multilayer ultra-low temperature cofiring dielectrics application.