ELECTRON-MICROSCOPIC OBSERVATION OF RAPIDLY COOLED ZRO2-3 MOL-PERCENTSM2O3 FROM THE MELT

Electron microscopic observation was made on ZrO2-3 mol % Sm2O3 specim ens prepared from the melt using two different cooling rates, namely r apid quenching using a hammer-anvil apparatus and free cooling-on a wa ter-cooled copper hearth. The observed microscopic features, such as f ully tetragonal grains with parallel twins or herringbone structure, a nti-phase boundary contrast in a dark-field image, tweed structure, et c., were found to be quite similar to those observed in similarly prep ared ZrO2-3 mol % Y2O3 specimens. It was specifically noted that the t weed structure, which requires atomic diffusion, was not suppressed by the rapid quenching, indicating a very fast growth rate. Trace analys is was also conducted on the tweed structure observed in freely cooled specimens.