Title: The role of pH and effect of calcination temperature on polymorphs and properties of iron oxide nanoparticles

Authors: J. Sharmila Justus; S. Dawn Dharma Roy; A. Moses Ezhil Raj; M. Bououdina

Addresses: Department of Physics and Research Centre, Nesamony Memorial Christian College, Marthandam – 629165, Tamil Nadu, India; Affiliated to Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli – 627012, Tamil Nadu, India; Department of Physics and Research Centre, Women's Christian College, Nagercoil – 629 001, Tamil Nadu, India ' Department of Physics and Research Centre, Nesamony Memorial Christian College, Marthandam – 629165, Tamil Nadu, India; Affiliated to Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli – 627012, Tamil Nadu, India ' Department of Physics and Research Centre, Scott Christian College (Autonomous), Nagercoil – 629 003, Tamil Nadu, India; Affiliated to Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli – 627012, Tamil Nadu, India ' Nanotechnology Centre, University of Bahrain, P.O. Box 32038, Zallaq, Kingdom of Bahrain

Abstract: Iron oxide nanoparticles were successfully synthesised by a facile solution approach employing iron (III) chloride (FeCl₃) as starting precursor and sodium hydroxide (NaOH) as reducing agent, followed by calcination in air at different temperatures viz. 400, 600 and 800°C for three hours. The range of calcination temperature has been chosen from thermogravimetry analysis. X-ray diffraction patterns clearly confirmed the structural transformation of cubic Fe₃O₄ to hexagonal α-Fe₂O₃ upon calcination. FTIR vibrational bands corresponding to Fe-O bondings in the tetrahedral and octahedral sites and their shift upon calcination confirmed the structural transitions. Scanning electron microscopy observations revealed agglomers meanwhile energy dispersive spectroscopy analysis confirm the elemental composition. Optical band gaps estimated from Tauc plots was found to vary with structural transformation. Electrical conductivity measurements with temperature were explained on the basis of fluctuation of ions in the B sites of Fe₃O₄ and deviation from stoichiometry in the case of α-Fe₂O₃.

Keywords: magnetic materials; nanoparticles; iron oxide; Fourier transform infrared spectroscopy; electron microscopy; optical properties; electrical conductivity.

DOI: 10.1504/IJNP.2019.097933

International Journal of Nanoparticles, 2019 Vol.11 No.1, pp.62 - 78

Received: 07 Jul 2018
Accepted: 10 Oct 2018
Published online: 22 Feb 2019 *

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