Amorphous zirconia gel was hydrothermally treated at 250 degrees C for
1-326 h in water and in NaOH water solution. Changes of the crystalli
te sizes and shapes were observed using TEM. The nature of these chang
es seems to be independent of the crystallization environment, but the
rate of the process is much faster in the NaOH solution. The mechanis
m of the crystal growth is suggested.