Table of Contents
ISRN Ceramics
Volume 2011, Article ID 406094, 8 pages
http://dx.doi.org/10.5402/2011/406094
Research Article

Microstructure, Mössbauer, and Optical Characterizations of Nanocrystalline 𝜶-Fe𝟐O𝟑 Synthesized by Chemical Route

1Department of Physics, University of Burdwan, Golapbag, Burdwan 713104, India
2Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700009, India
3Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Kolkata 700064, India
4Central Mechanical Engineering Research Institute, Durgapur 713209, India

Received 9 June 2011; Accepted 10 July 2011

Academic Editors: V. Fruth, H. Maiwa, W.-C. Oh, and W. Tseng

Copyright © 2011 Abhijit Banerjee et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Nanocrystalline α-Fe2O3 of crystallite sizes ranging from 18 nm to 54 nm has been prepared by sol gel process and postannealing the powder up to 500C. X-ray diffraction and transmission electron microscopy images have been used for determining the average crystallite sizes of the prepared samples. The Rietveld analysis reveals that the “as-prepared” α-Fe2O3 powders are not completely stoichiometric, and significant (~20%) oxygen vacancies are noticed in the α-Fe2O3 lattice. Oxygen atoms in as-prepared sample are significantly displaced and the lattice is heavily distorted. With increasing annealing temperature the lattice approaches towards the stoichiometric oxygen concentration and perfect lattice configuration. Mössbauer spectrum of the unannealed (as-prepared) α-Fe2O3 sample shows the superparamagnetic behavior at room temperature whereas all annealed samples show complete ferromagnetic behavior. Optical band gaps of these nanocrystalline α-Fe2O3 samples have been measured from UV-Vis spectroscopy and found to decrease from 2.65 eV to 2.50 eV, like an n-type semiconductor, with increasing annealing temperature up to 500C.