Mg-substituted ZnNb2O6–TiO2 composite ceramics for RF/microwaves ceramic capacitors

Abstract Microstructure and microwave dielectric properties of Mg-substituted ZnNb2O6–TiO2 microwave ceramics were investigated. Mg acted as a grain refining reagent and columbite phase stabilization reagent. With an increasing Mg content, the amount of ixiolite (Zn, Mg) TiNb2O8 decreased, and the amount of (Zn0.9Mg0.1)0.17Nb0.33Ti0.5O2 and columbite increased. ZnO–Nb2O5–1.75TiO2–5 mol.%MgO exhibited excellent dielectric properties (at 950 °C): ɛr = 35.6, Q × f = 16,000 GHz (at 5.6 GHz) and τf = −10 ppm/°C. The material was applied successfully to make RF/microwaves ceramic capacitor, whose self-resonance frequency was 19 GHz at low capacitance of 0.13 pF.