Surface analysis and corrosion behavior of zirconium samples implanted with yttrium and lanthanum

Zirconium specimens were implanted with yttrium and lanthanum ions with a fluence ranging from 1×1016 to 1×1017 ions/cm2 at approx. 130 °C, using a metal vapor vacuum arc source at an extraction voltage of 40 kV. The surfaces of the implanted samples were then analysed. The valence states of elements in implanted surface layer were analysed by X-ray photoelectron spectroscopy (XPS), which showed that yttrium existed in the form of Y2O3, and lanthanum existed in the form of La2O3. Depth distributions of elements in the implanted surface of samples were obtained by Auger electron spectroscopy (AES), which showed that the oxide film of zirconium substrate became thicker with increasing implantation fluence, the thicknesses of the oxide films reached the maximum approximately to the fluence of 1×1017 ions/cm2. Rutherford back-scattering indicates that a profile of La appears in Zr around the depth of 30 nm, which also indicates that a serious sputtering occurred during the (La+Y) 1×1017 ions/cm2 implantation. The potentiodynamic polarization technique was employed to evaluate the aqueous corrosion resistance of the implanted-zirconium samples in 0.6 M H2SO4. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zirconium compared with that of as-received zirconium when the fluence is smaller than 5×1016 (Y+La)/cm2. The mechanism of the corrosion behavior of the implanted-zirconium samples was discussed.