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

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 sinstered at 950 degreesC, and the polymorphic modification cordierite detected in the sintered sample was only stable hexagonal alpha-phase. The sintering densification process was performed mainly in the temperature range from 800 degreesC to 930 degreesC, 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). (C) 2004 Kluwer Academic Publishers.