Title: Synchrotron X-ray absorption spectroscopy study of disordered cation distribution of nanosized zinc ferrite powders

Authors: Thanit Tangcharoen; Chanapa Kongmark; Wantana Klysubun; Wisanu Pecharapa

Addresses: College of Nanotechnology, King Mongkut's Institute of Technology Ladkrabang (KMITL), Bangkok 10520, Thailand; Synchrotron Light Research Institute (SLRI), Nakhon Ratchasima 30000, Thailand ' Faculty of Science, Department of Materials Science, Kasetsart University (KU), Bangkok 10900, Thailand ' Synchrotron Light Research Institute (SLRI), Nakhon Ratchasima 30000, Thailand ' College of Nanotechnology, King Mongkut's Institute of Technology Ladkrabang (KMITL), Bangkok 10520, Thailand; Thailand and Center of Excellence in Physics (ThEP Center), CHE, 328 SiAyutthaya Rd., Bangkok 10400, Thailand

Abstract: The zinc ferrite (ZnFe₂O₄) powders of various nanoparticle sizes were synthesised at different milling times (0 to 24 h) of the as-combusted powders. The non-equilibrium site occupancy of zinc (Zn²⁺) and ferric (Fe³⁺) ions was investigated through Zn and Fe K-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra. The XRD and SEM strongly confirm the particle size of these ferrites decreasing with the increasing milling time. Compared with the bulk specimen of zinc ferrite, both XANES and EXAFS spectra of zinc ferrite powders clearly exhibit the large translocation of Zn²⁺ ions from the tetrahedral (A) sites to the octahedral (B) sites and the opposite translocation of some of Fe³⁺ ions without affecting the long-range structural order. Moreover, the curve-fitting analysis of Zn and Fe K-edge EXAFS spectra indicates that the degree of inversion increases as the particle size decreases resulting in significant differences in the magnetic behaviours.

Keywords: zinc ferrite powders; sol-gel auto-combustion; spinel structure; X-ray absorption near-edge structure; XANES; extended X-ray absorption fine structure; EXAFS; synchrotron XAS; X-ray absorption spectroscopy; disordered cation distribution; nanoparticles; nanotechnology; particle size; milling time; magnetic behaviour.

DOI: 10.1504/IJNT.2016.078546

International Journal of Nanotechnology, 2016 Vol.13 No.7, pp.545 - 560

Published online: 22 Aug 2016 *

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