Influence of the Preparation Technique on the Magnetic Characteristics of ε-Fe<sub>2</sub>O<sub>3</sub>-Based Composites

oleh: Dmitriy O. Testov, Kamil G. Gareev, Ivan K. Khmelnitskiy, Andrei Kosterov, Leonid Surovitskii, Victor V. Luchinin

Format: Article
Diterbitkan: MDPI AG 2022-12-01

Deskripsi

ε-Fe<sub>2</sub>O<sub>3</sub> is an iron(III) oxide polymorph attracting an increasing interest due to its unique magnetic properties combining extremely high coercivity and relatively large saturation magnetization. We review existing methods for the ε-Fe<sub>2</sub>O<sub>3</sub> synthesis focusing on synthesis speed, repeatability, manufacturability and purity of the final product. Samples of ε-Fe<sub>2</sub>O<sub>3</sub> have been synthesized using the two methods that appear the most promising: silica gel impregnation and microemulsion. In both cases, ε-Fe<sub>2</sub>O<sub>3</sub> and α-Fe<sub>2</sub>O<sub>3</sub> are present in the final product as attested by X-ray diffraction patterns and magnetic properties (maximum coercive force at 300 K~1 Tesla). Two different precursors, iron(III) nitrate and iron(II) sulfate, have been used in the silica gel impregnation method. Somewhat surprisingly, iron sulfate proved superior yielding ε-Fe<sub>2</sub>O<sub>3</sub> content of 69% in the total iron oxide product, compared to 25% for iron nitrate under the same synthesis conditions. These results pave the way for modifying the existing ε-Fe<sub>2</sub>O<sub>3</sub> synthesis methods aiming to increase the content of the epsilon phase in the final product and, consequently, improve its physicochemical properties.