RELATIONSHIP BETWEEN ORDERING RATIO AND MICROWAVE Q FACTOR ON INDIALITE/CORDIERITE GLASS CERAMICS

摘要

Millimeterwave dielectrics for wireless communications with high data transfer and radar system for Pre-Crash Safety System are expected to be developed on the microwave Q factor. Cordierite (Mg_2Al_4Si_5O_(18)), is a candidate for millimeter-wave dielectrics. Cordierite has two polymorphs due to ordering of Si and Al ions on (Si/Al)O_4 tertahedra: disordered high symmetry form called as indialite and ordered low symmetry form cordierite. It is well known that indialite is not synthesized by solid state reactions but crystallized from glass. In this paper, the crystal structures of cordierite glass ceramics composed by the two phases are analyzed by Rietveld method, and the site occupancies are confirmed by the volumes and covalencies based on the crystal structure. It was clarified that glass ceramics with high amount of disordered crystal structure has higher Q than one with ordered one. The properties: Qf = 148,919 GHz, r = 4.7 and TCf = -29 ppm/℃. This results are consistent with our insistency that is high symmetry brings high Q more than ordering.