A Thermal Decomposition Approach for the Synthesis of Iron Oxide Microspheres

Abstract

ABSTRACTIron oxide microspheres possess a wide range of applications in lithium storage batteries, sensors, photocatalysis, environmental remediation, magnetic resonance imaging and drug delivery. The most commonly used method for the preparation of iron oxide microspheres is hydrothermal synthesis. Besides this, other synthetic methods such as co-precipitation, electrostatic self- assembly, microwave and sol-gel have been reported. The reported synthetic methods usually require longer time (2 to 48 hours) and expensive experimental set up. In the present study, a novel low temperature thermal decomposition approach for the synthesis of iron oxide microspheres has been reported. Thermal decomposition of an iron-urea complex ([Fe(CON2H4)6](NO3)3) in a mixture of diphenyl ether and dimethyl formamide at 200 °C for 35 minutes leads to the formation of iron oxide microspheres. The microspheres were characterized using a variety of analytical techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS) and magnetometry. The XRD results indicated amorphous nature for the as prepared iron oxide, whereas after calcination at 500 °C, crystalline α-Fe2O3 phase is obtained. The SEM images indicated uniform spheres with an average diameter of 1.2 ± 0.3 μm. The DRS results too gave evidence for the formation of α-Fe2O3 on calcination of the microspheres at 500 oC.The field and temperature dependent magnetic measurement results indicated superparamagnetic behavior for the as prepared iron oxide microspheres indicating that the microspheres consist of iron oxide nanoparticles. On the other hand, an antiferromagnetic behavior was observed for the microspheres calcined at 500 °C. The present synthetic method is a novel method to produce magnetic materials with controlled morphologies.