Effect of cerium addition on phase transformation and microstructure of cordierite ceramics prepared by sol-gel method

摘要

Low-temperature sintering of cordierite ceramic depends on the phase transformation into cordierite and the properties depend on its microstructure. In the present work, the effect of cerium on the phase transformation and microstructure of cordierite ceramics prepared by sol-gel method is studied by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM) in order to lower the sintering temperature and improve the properties of cordierite ceramic with the addition of cerium. It is observed that the cerium addition obviously lowers the crystallization temperature of α-cordierite while slightly raises that of μ-cordierite. The lowest temperature for μ→α cordierite transformation, which approaches the crystallization temperature of μ-cordierite, is achieved in the sample containing 4 wt% of cerium, implying a possibility to lower the sintering temperature of cordierite ceramics. The Ce-contained ceramics show a biphasic microstructure that is dependent on sintering temperature. Sintered below 1300℃, a cordierite-CeO_(2) microstructure is present; while sintered at the temperature above 1300℃, appears a cordierite-glass microstructure, of which the amount of glass phase is limited to a small extent. Since the addition of 4 wt% cerium to this MgO-Al_(2)O_(3)-SiO_(2) system substantially enhances the densification of cordierite ceramics and lowers the sintering temperature to the level of around 1000℃, it makes the ceramics suitable for such applications, where the low-temperature sintering is required, as the substrates for electronic circuit and the catalytic supports (with oxygen storage capacity) for cleaning of automotive exhaust emissions.