Study of Radiation Defects in metal Mo and Ta by Mössbauer effect and EXAFS

Abstract

Abstract The implantation of 57Fe atoms into refractory metals Mo and Ta was studied by X-ray diffraction, Mossbauer spectroscopy, and EXAFS. When irradiated with 57Fe ions with energy of 1\xa0MeV and fluence of 5\xa0×\xa01016 ions/cm2, Fe implantation occurred to a depth of about 600\xa0nm, while creating an extremely strong level of radiation damage with DPA ≥100. Experimental data have confirmed the preservation of the original bcc crystal structure. The localization of 57Fe atoms in the Mo and Ta was studied by Mossbauer spectroscopy and by the EXAFS method in the Fe K-edge region. Both methods give consistent results. In Mo, Fe atoms are predominantly localized in substitutional positions with 1.4 atomic vacancies localized in the first coordinate sphere. Fe atoms in the Ta matrix have a more complex localization. The model spectra for typical atomic configurations of Fe in the Ta were calculated by the density functional theory. Comparison of the experimental spectra with the calculated ones showed that Fe atoms are localized in Ta in several positions, including interstitial and substitutional positions. It is shown that the EXAFS method more accurately determines the configurations of defects caused by irradiation.