CRYSTALLIZATION OF CERIA-DOPED ZIRCONIA IN LIQUID-MEDIA AT HIGH-TEMPERATURES

Amorphous 12CeO(2)-88ZrO(2) (mol.-%) gels were heated in liquid media such as water, methanol, and n-kexane above 200 degrees C. As initiall y prepared, the gels were amorphous, but after 5 h heating in methanol at 250 degrees C, tetragonal zirconia was identified by X-ray analysi s. An amorphous gel examined by differential thermal analysis on calci nation in ail showed crystallisation to the tetragonal form at 420 deg rees C. The crystallisation behaviour in liquid media could be adequat ely described by the surface chemical reaction controlled shrinking co re model. Crystallisation in water was much faster than in methanol an d n-hexane, but the sinterability of powder. prepared in water was poo l er than of that prepared in organic solvents. The addition ofrequisi te amounts of water to organic solvents was found useful in promoting crystallisation of gel without loss of powder sinterability. (C) 1996 The Institute of Materials.