STRUCTURAL STUDIES ON THE ZRO2-Y2O3 SYSTEM BY ELECTRON-DIFFRACTION AND ELECTRON-MICROSCOPY .2.

Oxygen-ion arrangements of 20-30 mol% Y//2O//3-ZrO//2 and 20-40 mol% Y//2O//3-HfO//2 in the high-temperature cubic phases have been investigated by electron diffraction and high-resolution electron microscopy. An analysis of the diffuse scattering appearing in electron-diffraction patterns provides a modulated structure model for each system, which consists of a positional modulation of oxygen ions and anti-phase boundaries. Modulated structures have been found to form micro-domains of several nm in diameter. Heat treatment indicates that ordered phases can exist below about 950 degree C in both systems.