Channeling in virgin and Yb implanted yttria stabilized zirconia crystals

Channeling experiments have been performed on [111] yttria stabilized zirconia (YSZ) single crystals with uniform Y concentration of 19 mol %. These crystals have the fluorite structure and contain 5% of oxygen vacancies. Various axial and planar, mixed (ZrO) and single crystallographic directions have been investigated. The results show a strong oxygen-oxygen vacancy interaction: the nearest neighbours of a vacancy (i.e. 6 oxygen atoms) are displaced from regular lattice sites by a distance greater than 0.5 A. The other oxygen atoms are also certainly displaced but by smaller quantities. No preferential direction could be evidenced for this displacement. A cation relaxation is not excluded by our results but its amplitude should not exceed ≅0.1 A . Some YSZ crystals were implanted with 1.2×1016 and 1.2×1017 Yb atoms/cm2 at 210 keV. The lattice parameters of YSZ and ytterbium stabilized zirconia are identical. For the low implantation dose, a full crystalline recovery is observed after a 1000°C annealing and Yb is 100% substitutional. A 1300°C annealing is required for the high implantation dose, for which the concentration ratio [Yb]/[Zr]≅1.1 in the implanted region. This region appears, after annealing, in full epitaxy with the substrate and the behaviour of Yb and Zr atoms is identical. However, the rather high minimum yields measured are indicative of strong atom relaxation.