AMORPHOUS AND NANOCRYSTALLINE ZrO2·Y2O3(15%) STUDIED BY EXTENDED X-RAY ABSORPTION FINE STRUCTURE

Chemical coprecipitated amorphous and nanocrystalline ZrO2·Y2O3(15%) was studied by Powder X-ray diffraction(XRD) and extended X-ray absorption fine structure(EXAFS). XRD result shows that the sample is an amorphous phase annealed below 300℃; and it crystallizes into cubic nanocrystalline zirconia at 500℃. EXAFS analysis indicates that the coordination number and bond length of Zr-O shell has not changed when transforming from amorphous into nanocrystalline. This suggests that at 300℃,it has formed the same nearest-neighbor local structure as at 900℃. For Zr-Zr(Y) shell, with the reducing of grain size, the coordination number decreases obviously: the bond length is shorter and the disorder becomes larger. This result suggests that the grain size effect is much stronger for more distant coordination shell (Zr-Zr ) than for the first nearest-neighbor shell(Zr-O).