Crystallisation of ceria doped zirconia in liquid media at high temperatures

Amorphous 12CeO₂-88ZrO₂ (mol.-%) gels were heated in liquid media such as water, methanol, and n-hexane above 200°C. As initially prepared, the gels were amorphous, but after 5 h heating in methanol at 250°C, tetragonal zirconia was identified by X-ray analysis. An amorphous gel examined by differential thermal analysis on calcination in air showed crystallisation to the tetragonal form at 420°C. The crystallisation behaviour in liquid media could be adequately described by the surface chemical reaction controlled shrinking core model. Crystallisation in wafer was much faster than in methanol and n-hexane, but the sinterability of powder prepared in water was poorer than of that prepared in organic solvents. The addition of requisite amounts of water to organic solvents was found useful in promoting crystallisation of gel without loss of powder sinterability.