Millimeter-wave dielectrics of indialite/cordierite glass ceramics: Estimating Si/Al ordering by volume and covalency of Si/Al octahedron

Abstract

Cordierite (Mg2Al4Si5O18) is a candidate for millimeter-wave dielectrics, and has two polymorphs due to ordering of Si and Al ions on Si/AlO4 tetrahedra: disordered high symmetry form called as indialite and ordered low symmetry form cordierite. Indialite/cordierite glass ceramics exhibited much higher Qf value of 200,000 GHz than conventional solid state reaction ceramics of 40,000 GHz, which were fabricated by crystallization of glass pellet. The glass ceramics having indialite as a dominant phase showed high Qf. The crystal phases are analyzed by Rietveld method. In this paper, the ordering ratios of indialite and cordierite are estimated by the volumes and covalencies of Si/AlO4 tetrahedra.