Preparation and microwave dielectric properties of SiO2 ceramics by aqueous Sol–Gel technique

► Highly reactive amorphous SiO2 nanospheres were synthesized at room temperature by a Sol–Gel method. ► SiO2 nanospheres were used to preparation of SiO2 ceramics and Excellent microwave properties of εr∼3.52, Q ƒ∼92400GHz and τƒ∼−14.5ppm/°C, were obtained. ► The optimum sintering temperature of SiO2 ceramics was reduced 125°C compared to a conventional solid-state method. ► The Q·ƒ and εr values of SiO2 ceramics are sensitive to the measured temperatures, which was explained by a composite dielectric model. Highly reactive amorphous SiO2 nanospheres were successfully synthesized at room temperature in atmosphere with a mean particle size of 174nm by a Sol–Gel method. SiO2 ceramics were prepared using SiO2 nanospheres and their microwave dielectric properties were investigated at different temperatures. Phase evolution, sintering characteristics and microstructures were detected by differential thermal analysis (DTA-TG) analysis, X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Excellent microwave properties of εr∼3.52, Q·ƒ∼92400GHz and τƒ∼−14.5ppm/°C, were obtained finally. The optimum sintering temperature of SiO2 ceramics was reduced 125°C by aqueous Sol–Gel process compared to a conventional solid-state method. The Q·ƒ and εr values of SiO2 ceramics are sensitive to the measured temperatures, which was explained by a simple composite dielectric model.