Dielectric properties and microstructure of TiO2 modified (ZnMg)TiO3 microwave ceramics with CaO–B2O3–SiO2

The low-fired (ZnMg)TiO3–TiO2 (ZMT–TiO2) microwave ceramics using low melting point CaO–B2O3–SiO2 as sintering aids have been developed. The influences of Mg substituted fraction on the crystal structure and microwave properties of (Zn1−xMgx)TiO3 were investigated. The result reveals that the sufficient amount of Mg (x ≥ 0.3) could inhibit the decomposition of ZnTiO3 effectively, and form the single-phase (ZnMg)TiO3 at higher sintering temperatures. Due to the compensating effect of rutile TiO2 (τf = 450 ppm/°C), the temperature coefficient of resonant frequency (τf) for (Zn0.65Mg0.35)TiO3–0.15TiO2 with biphasic structure was adjusted to near zero value. Further, CaO–B2O3–SiO2 addition could reduce the sintering temperature from 1150 to 950 °C, and significantly improve the sinterability and microwave properties of ZMT–TiO2 ceramics, which is attributed to the formation of liquid phases during the sintering process observed by SEM. The (Zn0.65Mg0.35)TiO3–0.15TiO2 dielectrics with 1 wt% CaO–B2O3–SiO2 sintered at 950 °C exhibited the optimal microwave properties: ε ≈ 25, Q × f ≈ 47,000 GHz, and τf ≈ ± 10 ppm/°C.