DEFECT STRUCTURE AND DIFFUSE-SCATTERING OF ZIRCONIA SINGLE-CRYSTALS DOPED WITH 7-MOL-PERCENT CAO

The defect structure of 7 mol% calcium-stabilized zirconia (CSZ) is de scribed in terms of a correlated distribution of microdomains within t he cubic matrix of CSZ. It is shown that the defect structure is very similar to that of 15 mol% CSZ. The defect structure consists of two t ypes of defects: microdomains based on a single oxygen vacancy with re laxed neighbouring ions and microdomains based on a pair of oxygen vac ancies separated by a3(1/2)/2 along [111]. Calculations show that a te tragonal distortion cannot explain the observed diffuse scattering. Se veral arguments suggest that the defect structure is not that of the P HI1 phase: first, the similarity of diffuse scattering of yttrium-stab ilized zirconia, for which no PHI1 phase exists; second, the diffuse s cattering of CSZ is almost identical from 4 mol% CSZ up to 20 mol% CSZ ; third, the diffuse scattering is temperature dependent; and fourth, a direct comparison of single-crystal intensities of the PHI1 phase wi th the intensity of diffuse scattering.