The effects of adding cordierite seed crystals to the mixture of alumina sol, silica sol and Mg（OH）2 fine particle on densification and change of crystal phase were investigated. When seed crystals were not added, Mg2SiO4, MgSiO3, MgAl2O4, and amorphous substances were formed during heating, and these reactions produced cordierite polycrystals with low thermal expansion at 1225 ℃ or higher. On the other hand, when seed crystals were added, cordierite was directly crystalized from the amorphous substances without passing through the intermediate products. In the cordierite sintered body prepared by adding seed crystals, the domain diameter was 15 μm or less, so that the occurrence of microcracks could be suppressed. Therefore, the coefficient of thermal expansion at 30-900 ℃ showed a constant value of 1.7×10－6 K－1. In addition, the coefficient of thermal expansion at 0－50 ℃ is almost zero, and it is expected to be applied to various industrial applications.

View full abstract