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-x Mg (x) )TiO3 were investigated. The result reveals that the sufficient amount of Mg (x a parts per thousand yen 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 (tau(f) = 450 ppm/A degrees C), the temperature coefficient of resonant frequency (tau(f)) for (Zn0.65Mg0.35)TiO3-0.15TiO(2) with biphasic structure was adjusted to near zero value. Further, CaO-B2O3-SiO2 addition could reduce the sintering temperature from 1150 to 950 A degrees 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)TiO3-0.15TiO(2) dielectrics with 1 wt% CaO-B2O3-SiO2 sintered at 950 A degrees C exhibited the optimal microwave properties: epsilon A a parts per thousand A 25, Q x f a parts per thousand 47,000 GHz, and tau(f) a parts per thousand +/- A 10 ppm/A degrees C.