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

Abstract

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 ε_r = 5.6–13.5, Q × f = 13,000–25,000 GHz, and τ_f =− 97.3 to − 38.3 ppm/°C, which made the compounds promising for multilayer ultra-low temperature cofiring dielectrics application.