Formation of spherical and rod-shaped ε-Fe2O3 nanocrystals with a large coercive field

Jian Jin; Kazuhito Hashimoto; Shin-ichi Ohkoshi

doi:10.1039/B416554C

Formation of spherical and rod-shaped ε-Fe₂O₃nanocrystals with a large coercive field

Jian Jin,^a Kazuhito Hashimoto*^a and Shin-ichi Ohkoshi*^ab

* Corresponding authors

^a Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
E-mail: ohkoshi@light.t.u-tokyo.ac.jp, hashimoto@light.t.u-tokyo.ac.jp

^b PRESTO, JST, 4-1-8 Honcho Kawaguchi, Saitama, Japan

Abstract

ε-Fe₂O₃/SiO₂ composites were prepared by combination of reverse micelle and sol–gel methods. The samples were characterized by X-ray powder diffraction and transmission electron microscopy. A spherical ε-Fe₂O₃ nanoparticle of 16 nm diameter was obtained at a sintering temperature of 1050 °C. When an appropriate amount of IIA metal ion (Sr²⁺ or Ba²⁺) was added to this system, ε-Fe₂O₃ particles of larger particle size up to 100–200 nm were produced with rod-like shape under a 1000 °C sintering temperature. Magnetic measurements showed that the rod-like ε-Fe₂O₃ particles exhibited a giant coercive field up to 2.0 T (20 kOe). The reason why such a rod-like ε-Fe₂O₃ particle is obtained is that (1) the formation of IIA metal ion-containing components around the ε-Fe₂O₃ surface helps to stabilize and extend the existence of ε-Fe₂O₃ as metastable phase during sintering, and (2) the selective adsorption of IIA metal ions on the tetrahedral site of the Fe₂O₃ surface leads to the anisotropic crystal growth of ε-Fe₂O₃ nanocrystals.

Article information

https://doi.org/10.1039/B416554C

Article type

Paper

Submitted

28 Oct 2004

Accepted

09 Dec 2004

First published

17 Jan 2005

Download Citation

J. Mater. Chem., 2005,15, 1067-1071

Permissions

Request permissions

Formation of spherical and rod-shaped ε-Fe₂O₃ nanocrystals with a large coercive field

J. Jin, K. Hashimoto and S. Ohkoshi, J. Mater. Chem., 2005, 15, 1067 DOI: 10.1039/B416554C

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Journal of Materials Chemistry