Sintering and crystallization of cordierite glass ceramics for high frequency multilayer chip inductors

Cordierite-based ceramics were developed by sintering a glass selected from MgO–Al2O3–SiO2 system with an aim to use the material as high frequency chip inductors. A small amount of B2O3 and P2O5 were added to optimize the preparation conditions. The glass powder and sintered bodies were characterized by different analytical techniques such as TG-DTA analysis, X-ray diffraction, transmission and scanning electron microscopy. Pellets uniaxially pressed from the glass power could be sintered well at 950 °C having a density of above 99% theoretically, dielectric constant of 5.5, dielectric loss of 0.001 and thermal expansion coefficient of 26.7×10−7 °C−1 (20–400 °C). Crystalline phases in this sintered sample are predominantly α-cordierite (hexagonal high cordierite) and trace amount of μ-cordierite. SEM depicted a uniformly dense microstructure with crystals of granular habit in the sintered sample.