Millimeter-Wave Dielectric Properties of Cordierite/Indialite Glass Ceramics

Abstract

Millimeter-wave wireless communications with high data transfer and radar system for Pre-Crash Safety System have been developed recently. Cordierite (Mg 2 Al 4 Si 5 O 18 ) is one of the silicates with good millimeter-wave dielectric properties. Cordierite has two polymorphs: cordierite and indialite. Cordierite is of low symmetry form with ordered structure, and indialite is of high symmetry form with disordered structure. In this study, indialite/cordierite glass ceramics are fabricated with good millimeter-wave properties. The Qf values are dependent on the amount of indialite phase and crystallization conditions. Indialite with high symmetry showed higher Qf values than cordierite with low symmetry. This result clearly shows that high symmetry results in high Qf when the samples are prepared under the same crystallization conditions. However, these glass ceramics are very difficult to make under the same conditions because of non-uniform crystallization. These dielectric glass ceramics show high Qf values of >200,000 GHz, low dielectric constant ε r = 4.7, and TCf = -27 ppm/°C.