Local ordering of oxygen vacancies in cubic zirconia (ZrO2) stabilized with yttria (Y2O2) and magnesia (MgO) I. Electron diffuse scattering study

Diffuse scattering, being highly intensive and confined in reciprocal space to a regular geometric surface exhibiting the translation symmetry of the bcc reciprocal lattice, is observed by electron diffraction from partially stabilized zirconia with Y2 O3 and MgO. This material is a structural ceramic having potential applications at high temperatures (> 1000°C). A three-dimensional geometric model of the diffuse scattering distributed in reciprocal space is constructed and an analytical equation corresponding to this model is established. In the reciprocal-space unit cell, the diffuse scattering distributes on the surfaces of eight rotational ellipsoids whose rotational axes are along the (111) directions of the bcc reciprocal lattice. Possible sources regarding the formation of the diffuse scattering are discussed. It is concluded that local ordering of oxygen vacancies in the cubic phase matrix, corresponding possibly to a transition state changing from the disordered cubic fluorite structure to an ordered superstructure, is the dominant factor that is responsible for the observed characteristic diffuse scattering.