Ultra-low temperature fired glass-free Li_2O-MO-WO_3 (M = Co, Ni, Ca, Ba) microwave dielectric ceramics

摘要

The Li~(2)O–MO–WO~(3)(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 Li~(2)O–MO–WO~(3)(M = Co, Ni) consist of CoWO~(4)(NiWO~(4)), Li~(2)WO~(4)and Li~(2)W~(2)O~(7)phases while Li~(2)O–MO–WO~(3)(M = Ca, Ba) comprises CaWO~(4)(BaWO~(4)) and Li~(2)WO~(4)phases. The porosity and phase constitution acted as a controlling factor of dielectric constant in the Li~(2)O–MO–WO~(3)(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.