The microwave dielectric properties of (1 − x)BaTi4O9–xBaZn2Ti4O11 ceramics were investigated by solid-state reaction technique for obtaining high-Q dielectric ceramics in BaO–ZnO–TiO2 system. And they were strongly determined by the chemical composition. As x was increased from 0.05 to 0.50, BaZn2Ti4O11 phase formed more and more. Therefore, the εr decreased from 37.3 to 32.8 and the Q × f values first raised from 45,300 GHz to 60,600 GHz (x = 0.30) and then started to decline to 58,700 GHz (x = 0.40), and the τf values varied gradually from 12 ppm/°C to − 13 ppm/°C. 0.7BaTi4O9–0.3BaZn2Ti4O11 ceramics sintered at 1240 °C for 3 h had excellent comprehensive microwave dielectric properties: εr = 34.2, Q × f = 60,600 GHz and τf = − 2 ppm/°C.Highlights►BaO–xZnO–4TiO2 ceramics was investigated by solid-state reaction technique. ►The two-phase system BaTi4O9–BaZn2Ti4O11 was formed. ►Excellent comprehensive microwave dielectric properties were obtained.

In this paper, the BaO-0.6ZnO-xTiO2 ceramics with x=2.5–2.8 have been prepared by the conventional solid-state ceramic route for the purpose of investigating the effect of TiO2 content on the microwave dielectric properties. The XRD results showed that the main crystal phase in the sintered ceramics was Ba4ZnTi11O27 and that the additional phases: Ba2ZnTi5O13 and BaZn2.03Ti3.93O10.89 were presented, depending on the TiO2 contents. The SEM photographs of the samples sintered at 1200°C for 2 h showed a high compact microstructure. Because the phase composition of ceramics samples was changed with TiO2 content, the dielectric constant (ɛr), the quality factor values (Q×f) and the temperature coefficient of resonant frequency (τf) were first increased, continuously came up to a peak value, and then let up. It was lucky to find that the sample with composition BaO-0.6ZnO-2.7TiO2 had both the maximum dielectric constant εr =36.1 and the maximum Q×f value of 29320 GHz, and more importantly, it had an acceptable temperature coefficient of resonant frequency τf =10.45 ppm/°C.