Sintering characteristics and crystallization for sol–gel-derived powders for low-dielectric and low-temperature sintering ceramics

Abstract

Samples in the MgO–Al₂O₃–SiO₂ system were prepared by the sol–gel technique. The coalescence, sintering characteristics, and crystallization were investigated by X-ray diffraction, thermal analysis, and scanning electron microscopy. The dielectric properties and density were measured with an impedance analyzer. Results demonstrated that the obtained cordierite powders synthesized with the sol–gel method distribute uniformly and its effective size is 474 nm. The glass powder could be sintered at 950 °C, and the polymorphic modification cordierite detected in the sintered sample was only stable hexagonal α-phase. The sintering densification process was performed mainly in the temperature range from 800 °C to 930 °C, and follows the viscous floating principle. The dielectric constant of the sintered body is 4.2 and its dielectric loss is lower than 0.001 at high frequency (1.5 GHz).