Effect of Impurity in Starting Kaolin Materials on Sintering Behavior of Cordierite Ceramics.

Effect of impurities in kaolin materials on the sintering behavior of the cordierite ceramics was studied. Three kinds of kaolins were used, that is, Georgia kaolin, Chinese kaolin and New Zealand kaolin. Georgia kaolin without α-quartz and cristobalite only gave a dense sintered body. α-quartz contained in both Chinese kaolin and New Zealand kaolin would retard the densification of sintered bodies. In the case of Chinese kaolin, chemical components except for MgO, Al2O3 and SiO2 in mixture accelerated the generation of liquid phase at above 1300°C and apparent porosity in sintered body decreased by liquid phase sintering. In the case of New Zealand kaolin, cristobalite and α-cordierite crystallized at higher temperature than that of Georgia kaolin and Chinese kaolin.