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

Low-temperature sintering of cordierite ceramic depends on the phase transf ormation into cordierite and the properties depend on its microstructure. I n the present work, the effect of cerium on the phase transformation and mi crostructure of cordierite ceramics prepared by sol-gel method is studied b y 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. I t is observed that the cerium addition obviously lowers the crystallization temperature of alpha -cordierite while slightly raises that of mu -cordier ite. The lowest temperature for mu --> alpha cordierite transformation, whi ch approaches the crystallization temperature of mu -cordierite, is achieve d in the sample containing 4 wt% of cerium, implying a possibility to lower the sintering temperature of cordierite ceramics. The Ce-contained ceramic s show a biphasic microstructure that is dependent on sintering temperature . Sintered below 1300 degreesC, a cordierite-CeO2 microstructure is present ; while sintered at the temperature above 1300 degreesC, appears a cordieri te-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-Al2O3-SiO2 sy stem substantially enhances the densification of cordierite ceramics and lo wers the sintering temperature to the level of around 1000 degreesC, it mak es the ceramics suitable for such applications, where the low-temperature s intering is required, as the substrates for electronic circuit and the cata lytic supports (with oxygen storage capacity) for cleaning of automotive ex haust emissions. (C) 2001 Kluwer Academic Publishers.