Fabrication, sintering and characterization of cordierite glass-ceramics for low temperature co-fired ceramic substrates from kaolin

Non-stoichiometric alpha-cordierite glass ceramic doped with H3BO3 and NH4H2PO4 as additives has been fabricated successfully from sandy kaolin as low temperature co-fired ceramics (LTCC) substrate materials. The sintering and crystallization behaviors of the glass-ceramics were investigated by the differential scanning calorimetry, X-ray diffraction, and field emission scanning electron microscope. In addition, various physical properties were characterized, such as dielectric properties, thermal expansion and flexural strength. The results indicated that there was only onefold alpha-cordierite formed from MgO-Al2O3-SiO2 glasses in the temperature range from 875 to 925 A degrees C. The glass-ceramics could been highly densified at any experimental temperature and they showed excellent properties: low dielectric constants in the range of 5.5-7.5, low dielectric losses in the range of 0.015-0.025, low coefficients of thermal expansion between 1.22-4.32 x 10(-6) K-1 and applicable flexural strength at the level from 110 to 145 MPa. All of the performance qualified cordierite glass ceramic to be used as potential LTCC substrate.