Imam N G, Harfouche Messaoud, Azab A A, Solyman S
Experimental Nuclear Physics Department (Solid State Laboratory), Nuclear Research Center (NRC), Egyptian Atomic Energy Authority (EAEA), Cairo 13759, Egypt.
Synchrotron-Light for Experimental and Scientific Applications in the Middle East (SESAME), PO Box 7, Allan 19252, Jordan.
J Synchrotron Radiat. 2022 Sep 1;29(Pt 5):1187-1197. doi: 10.1107/S1600577522006439. Epub 2022 Jul 15.
γ-Irradiation and synchrotron-radiation-based X-ray absorption fine-structure (XAFS) spectroscopy have been used to induce structure disorder through the interaction of γ-rays (200 kGy) with fabricated Mn-doped ZnO nanoparticles (NPs) and then to examine thoroughly the resultant structural change. The extracted electronic/fine XAFS structural parameters reflect a compositional and γ-irradiation co-dependence. The average crystal structure of samples prepared by the sol-gel method was investigated by X-ray diffraction (XRD). A detailed structural XRD data analysis was carried out by applying a Rietveld refinement using the MAUD program. XAFS spectra were collected at the Zn K-edge (9659 eV) in transmission mode and at the Mn K-edge (6539 eV) in fluorescence mode. Direct evidence of the solubility of Mn ions in the ZnO structure was demonstrated by fitting the extended-XAFS (EXAFS) signal. Near-edge XAFS (XANES) analysis provided the oxidation states of Zn and Mn ions through fingerprint XANES spectra of the sample along with those of standard compounds. Linear combination fitting showed that the most fit chemical forms of Zn and Mn in the samples are ZnO and MnO, respectively. The oxidation states of both Zn and Mn XAFS absorbers were confirmed from pre-edge fitting. The results of the magnetic measurements were explained in light of the average and electronic/local structural information obtained from XRD, XANES and EXAFS techniques. The magnetic properties of the samples translate into an induced change in the average crystal and electronic/local structures upon Mn concentration change and γ-irradiation. XRD confirmed the successful preparation of hexagonal Mn-doped ZnO NPs with a crystallite size in the range 33-41 nm. Both XRD and EXAFS analysis detected a minor amount of MnO as a secondary phase. XANES and EXAFS provided information exploring the outstanding potential of the utilized protocol for detecting precisely the presence of the secondary phase of MnO, which changes with Mn content (x). Mean-square relative displacement (σ) values extracted from the EXAFS fitting were found to grow for Zn-Zn/Mn paths demonstrating the substitution of Mn/Zn into Zn crystal sites. The EXAFS analysis explains the reasons behind the enhancement in the magnetic properties and shows that the Mn doping content at x = 0.05 produces the most local atomic disorder in ZnO NPs. There is a strong harmony among the XRD, XANES, EXAFS and magnetization behavior of the Mn-doped ZnO NPs. Maximum magnetization was acquired at an Mn content of 0.05. γ-Ray-irradiated ZnMnO NPs are recommended as optimized candidates for showing the diversity of the applications.
基于γ辐射和同步辐射的X射线吸收精细结构（XAFS）光谱已被用于通过γ射线（200 kGy）与制备的锰掺杂氧化锌纳米颗粒（NPs）相互作用来诱导结构无序，然后全面研究由此产生的结构变化。提取的电子/精细XAFS结构参数反映了成分和γ辐射的共同依赖性。通过X射线衍射（XRD）研究了采用溶胶-凝胶法制备的样品的平均晶体结构。使用MAUD程序通过Rietveld精修对XRD数据进行了详细的结构分析。在透射模式下于锌K边（9659 eV）收集XAFS光谱，在荧光模式下于锰K边（6539 eV）收集。通过对扩展XAFS（EXAFS）信号进行拟合，证明了锰离子在氧化锌结构中的溶解性的直接证据。近边XAFS（XANES）分析通过样品以及标准化合物的指纹XANES光谱提供了锌和锰离子的氧化态。线性组合拟合表明，样品中锌和锰最匹配的化学形式分别是ZnO和MnO。通过边前拟合确认了锌和锰XAFS吸收体的氧化态。根据从XRD、XANES和EXAFS技术获得的平均和电子/局部结构信息解释了磁性测量结果。样品的磁性在锰浓度变化和γ辐射时转化为平均晶体和电子/局部结构的诱导变化。XRD证实成功制备了六方晶系的锰掺杂氧化锌纳米颗粒，其微晶尺寸在33 - 41 nm范围内。XRD和EXAFS分析均检测到少量MnO作为第二相。XANES和EXAFS提供了信息，探索了所采用的方案在精确检测MnO第二相存在方面的巨大潜力，该第二相会随锰含量（x）而变化。从EXAFS拟合中提取的均方相对位移（σ）值对于锌-锌/锰路径而言增大，表明锰/锌替代进入了锌晶体位点。EXAFS分析解释了磁性增强背后的原因，并表明在x = 0.05时的锰掺杂含量在氧化锌纳米颗粒中产生了最大的局部原子无序。锰掺杂氧化锌纳米颗粒的XRD、XANES、EXAFS和磁化行为之间存在很强的协调性。在锰含量为0.05时获得了最大磁化强度。推荐γ射线辐照的ZnMnO纳米颗粒作为展示应用多样性的优化候选材料。
