Abstract

Radiation defects arising from the high-dose implantation of ⁵⁷Fe⁺ ions into matrices of refractory Mo and Ta metals are studied by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy in the region of the Fe K-edge Fe. The concentration of Fe atoms, which is calculated using the SRIM program, is 2.5 at % at a depth of ≈300 nm. The concentration of radiation-induced defects exceeds 100 dpa. The positions of Fe atoms are determined in the samples after implantation and additional annealing at 700°C. In Mo, Fe atoms are predominantly located in substitution positions in a body-centered cubic (bcc) crystal lattice. An analysis of the EXAFS spectra shows that, on average, 1.4 atomic vacancies are in the first coordination sphere of Fe, which corresponds to a vacancy concentration of about 24 at %. In the Ta matrix, Fe atoms are located in a more complex manner. To analyze the data, model EXAFS spectra are calculated for typical atomic configurations of Fe atoms in a Ta matrix, which form as a result of irradiation. Relaxation of the crystal environment of Fe atoms is taken into account by the density-functional-theory method. Comparison of the experimental spectra with the calculated ones shows that Fe atoms are located in several positions in Ta, including interstitial and substitution positions. Annealing leads to a change in the coordination and partial segregation of Fe atoms. The EXAFS data are consistent with previously published Mössbauer-spectroscopy data. It is demonstrated that the EXAFS method makes it possible to more accurately determine the configurations of defects arising from irradiation.

中文翻译：

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EXAFS 研究钼和钽金属中辐射引起的缺陷

摘要

通过在 Fe K区域的扩展 X 射线吸收精细结构 (EXAFS) 光谱学研究了由⁵⁷ Fe ⁺离子高剂量注入难熔 Mo 和 Ta 金属基体引起的辐射缺陷边铁。使用 SRIM 程序计算的 Fe 原子浓度为 2.5 at %，深度约为 300 nm。辐射引起的缺陷浓度超过 100 dpa。在注入和 700°C 的附加退火后，确定样品中 Fe 原子的位置。在 Mo 中，Fe 原子主要位于体心立方 (bcc) 晶格中的取代位置。对 EXAFS 光谱的分析表明，平均而言，1.4 个原子空位位于 Fe 的第一个配位层中，这对应于约 24 at% 的空位浓度。在 Ta 基体中，Fe 原子的位置更为复杂。为了分析数据，模型 EXAFS 光谱计算了 Ta 基质中 Fe 原子的典型原子构型，该构型是辐照的结果。通过密度泛函理论方法考虑了Fe原子晶体环境的弛豫。实验光谱与计算光谱的比较表明，Fe原子位于Ta中的几个位置，包括间隙和取代位置。退火导致Fe原子的配位和部分偏析发生变化。EXAFS 数据与先前发表的穆斯堡尔光谱数据一致。结果表明，EXAFS 方法可以更准确地确定辐照引起的缺陷配置。退火导致Fe原子的配位和部分偏析发生变化。EXAFS 数据与先前发表的穆斯堡尔光谱数据一致。结果表明，EXAFS 方法可以更准确地确定辐照引起的缺陷配置。退火导致Fe原子的配位和部分偏析发生变化。EXAFS 数据与先前发表的穆斯堡尔光谱数据一致。结果表明，EXAFS 方法可以更准确地确定辐照引起的缺陷配置。