Henry Killian, Ahlburg Jakob Voldum, Andersen Henrik L, Granados-Miralles Cecilia, Stingaciu Marian, Saura-Múzquiz Matilde, Christensen Mogens
Center for Materials Crystallography (CMC), Department of Chemistry and iNANO, Aarhus University, Aarhus, C-8000, Denmark.
Université de Lorraine, CNRS, IJL, Nancy, F-54000, France.
J Appl Crystallogr. 2022 Oct 1;55(Pt 5):1336-1350. doi: 10.1107/S1600576722008123.
Powder X-ray diffraction (PXRD) and neutron powder diffraction (NPD) have been used to investigate the crystal structure of CoFeO nanoparticles prepared different hydro-thermal synthesis routes, with particular attention given to accurately determining the spinel inversion degrees. The study is divided into four parts. In the first part, the investigations focus on the influence of using different diffraction pattern combinations (NPD, Cu-source PXRD and Co-source PXRD) for the structural modelling. It is found that combining PXRD data from a Co source with NPD data offers a robust structural model. The second part of the study evaluates the reproducibility of the employed multipattern Rietveld refinement procedure using different data sets collected on the same sample, as well as on equivalently prepared samples. The refinement procedure gives reproducible results and reveals that the synthesis method is likewise reproducible since only minor differences are noted between the samples. The third part focuses on the structural consequences of (i) the employed heating rate (achieved using three different hydro-thermal reactor types) and (ii) changing the cobalt salt in the precursors [aqueous salt solutions of Co(CHCOOH), Co(NO) and CoCl] in the synthesis. It is found that increasing the heating rate causes a change in the crystal structure (unit cell and crystallite sizes) while the Co/Fe occupancy and magnetic parameters remain similar in all cases. Also, changing the type of cobalt salt does not alter the final crystal/magnetic structure of the CoFeO nanoparticles. The last part of this study is a consideration of the chemicals and parameters used in the synthesis of the different samples. All the presented samples exhibit a similar crystal and magnetic structure, with only minor deviations. It is also evident that the refinement method used played a key role in the description of the sample.
粉末X射线衍射（PXRD）和中子粉末衍射（NPD）已被用于研究通过不同水热合成路线制备的CoFeO纳米颗粒的晶体结构，特别关注准确确定尖晶石的反演程度。该研究分为四个部分。在第一部分中，研究重点在于使用不同衍射图谱组合（NPD、铜源PXRD和钴源PXRD）进行结构建模的影响。结果发现，将来自钴源的PXRD数据与NPD数据相结合可提供一个可靠的结构模型。研究的第二部分评估了使用相同样品以及等效制备的样品上收集的不同数据集所采用的多图谱Rietveld精修程序的可重复性。精修程序给出了可重复的结果，并表明合成方法同样具有可重复性，因为在样品之间仅注意到微小差异。第三部分重点关注（i）所采用的加热速率（使用三种不同类型的水热反应器实现）和（ii）在合成中改变前驱体中的钴盐[Co(CH₃COOH)₂、Co(NO₃)₂和CoCl₂的盐水溶液]的结构后果。结果发现，提高加热速率会导致晶体结构（晶胞和微晶尺寸）发生变化，而在所有情况下Co/Fe占有率和磁参数保持相似。此外，改变钴盐的类型不会改变CoFeO纳米颗粒的最终晶体/磁结构。本研究的最后一部分是对合成不同样品所使用的化学物质和参数的考虑。所有呈现的样品都表现出相似的晶体和磁结构，只有微小偏差。同样明显的是，所使用的精修方法在样品描述中起了关键作用。
