Structural studies on the ZrO2-Y2O3system by electron diffraction and electron microscopy. II

For pt.I see Japan. J. Appl. Phys., vol.24, p.401 (1985). Oxygen-ion arrangements of 20-30 mol.% Y 2 O 3 -ZrO 2 and 20-40 mol.% Y 2 O 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. The oxygen-ion modulation is expressed by a square transverse wave whose wavenumber vector is q=( pi /a 0 )(110). Anti-phase boundaries lie parallel to the (112) planes at intervals of five and seven times the (112) spacing of the ZrO 2 -Y 2 O 3 and the HfO 2 -Y 2 O 3 crystals, respectively. These 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 degrees C in both systems.