COPPER, IRON AND ZIRCONIUM IMPLANTATION INTO POLYCRYSTALLINE ALPHA-AL2O3

Polycrystalline alpha-Al2O3 samples have been implanted by 10(17) Zr, Fe or Cu ions/cm2 at 110 keV in order to form oxide precipitates in the near-surface region after annealing in air. A chemical and microstructural characterization has been performed on the as-implanted surface and on the samples annealed in the temperature range from 600 to 1600-degrees-C. The nature of the chemical phases and the precipitate evolution have been characterized by combining RBS, XPS, GXRD, CEMS, TEM and SEM techniques. XPX, CEMS and TEM experiments on as-implanted specimens detect copper, iron and zirconium as Cu0 (small metallic precipitates), Fe0 (small alpha-iron precipitates), Fe(II) (associated with FeAl2O4), and Fe(IV) (metastable state), Zr0 and Zr(IV) (ZrO2) in the as-implanted region. Analyses carried out after heat treatments between 600 and 1000-degrees-C indicate a complete surface oxidation in this temperature range. Additionally, some precipitates appear along grain boundaries. Annealing at temperatures ranging from 1000 to 1600-degrees-C leads to drastic surface composition changes. The stability and size of the different observed precipitates (ZrO2, AlFeO3, Fe2O3, Fe3O4, CuO, CuAl2O4) strongly depend on the annealing temperature.