THE EFFECT OF Y-ION IMPLANTATION ON THE OXIDATION OF BETA-NIAL

The influence of Y-ion implantation on the oxidation of beta-NiAl sing le crystals has been investigated using SEM TEM, and STEM. Y ions havi ng an energy of 70 keV were implanted with a concentration of 5 x 10(1 6) ions/cm(2). The oxidation experiments were per;formed in air at 122 3 K. Y-ion implantation resulted in a 45-nm disordered layer. Oxidatio n of Y-implanted beta-NiAl leads to the formation of a fine-grain laye r, consisting of gamma-Al2O3 containing Y and a theta-Al2O3 layer. Aft er further oxidation the metastable Al2O3 transformed into alpha-Al2O3 , which started at the metal-oxide interface. Y-Al-garnet (YAG) partic les were observed and Y segregation to alpha-Al2O3 grain boundaries ha s been detected.