Microstructural behavior of γ-Fe2O3 formation in reactions between layered iron oxychloride and sodium n-pentoxide

Microstructural behavior of γ-Fe2O3 formation in reactions between FeOCl and n-C5H11ONa was thoroughly investigated. Reactions were conducted at 50–150 °C for 3 days in an autoclave using n-C5H11OH as a solvent. X-ray diffraction (XRD) patterns and infrared (IR) spectra of the products suggested the crystallization of γ-Fe2O3 besides the formation of n-pentoxy derivatives of FeOCl. Scanning electron microscopic observation revealed that the FeOCl particles were divided into thin sheets upon reaction. The selected area electron diffractions (SAED) of the sheets revealed the crystallization of γ-Fe2O3 at even 80 °C, apparently due to the fact that the γ-Fe2O3 crystallization process involved a collapse from n-pentoxide derivatives with large separations between two adjacent layers. In the reaction at 150 °C, a part of the sheets was converted into highly oriented polycrystalline γ-Fe2O3 in improved crystallinity, and the SAED clearly showed that an oriented transformation with a crystallographic relationship of FeOCl (010)//γ-Fe2O3 (110) occurred. The reaction at 120 °C, on the contrary, led to the formation of randomly oriented γ-Fe2O3 crystallites within a sheet.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Formation of n-pentoxide derivatives of FeOCl in all the reactions. ► γ-Fe2O3 crystallites formation in the reactions at 80 and 120 °C. ► Highly oriented polycrystalline γ-Fe2O3 formation of in the reaction at 150 °C. ► γ-Fe2O3 crystallized from the n-pentoxide derivatives of FeOCl. ► Crystallographic FeOCl (010)//γ-Fe2O3 (110) relationship in the reaction at 150 °C.