Phase composition, magnetic properties and thermal behavior of a novel Fe2O3-SiO2 composite material

An Fe2O3-SiO2 composite was prepared by controllable Fe3+ and SIO32- hydrolysis. Scanning (SEM) and transmitting (TEM) electron microscopy images showed particles with an average size of 10-30 nm composed of an iron-containing core covered with a silica shell. The FT-IR, vibrating sample magnitometer (VSM), thermogravimetric analysis and Mossbauer spectroscopy study confirmed that the core consisted of ferrihydrite. Heating at 300 degrees C did not result in any noticeable phase transitions, whereas 800 degrees C heating caused the formation of the maghemite gamma-Fe2O3 phase. Such improvement of the thermal stability of maghemite is promising for development of heat-resistant magnetic materials. (C) 2015 Elsevier B.V. All rights reserved.