Characterization and magnetic properties of hollow α-Fe2O3 microspheres obtained by sol gel and spray roasting methods

L. De Los Santos Valladares, A. Bustamante Domínguez, L. León Félix, J. B. Kargin, D. G. Mukhambetov, A. L. Kozlovskiy, N. O. Moreno, J. Flores Santibañez, R. Castellanos Cabrera, C. H.W. Barnes

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6 Scopus citations

Abstract

In this work, we characterize the hollow hematite (α-Fe2O3) micro spheres obtained by two non-template techniques: i) sol gel and ii) spray roasting process. Both techniques allow the production of high yield hollow hematite spheres up to 100 g for the case of sol gel and up to 500 kg for the case of spray roaster process. The samples were characterized by X-ray diffraction, scanning electron microscopy and Mössbauer spectroscopy. The results indicate nearly uniform hollow spheres with diameters of around 1–1.5 μm and consisting of polycrystalline hematite. The Mӧssbauer spectroscopy reveals the signal change of quadrupole shift values evidencing the occurrence of the Morin transition and that the samples show an antiferromagnetic order at 77 K as in bulk hematite. The Morin temperature (TM) for both samples was obtained from the measurements of the magnetic moments as a function of the temperature in zero field cooling (ZFC) and field cooling (FC) modes. The values of TM for both samples are lower than that reported for bulk hematite (TM(bulk) = 263 K). Remarkably, the ZFC and FC loops do not overlap in both samples, revealing irreversible Morin transition. However, the sample obtained by sol gel presents thermal hysteresis with TM values of 260 K (in ZFC) and 248 K (FC). Whereas, the sample obtained by spray roaster process presents complete irreversibility and TM values of 252 K (in ZFC) and 242 K (in FC).

Original languageEnglish
Pages (from-to)483-491
Number of pages9
JournalJournal of Science: Advanced Materials and Devices
Volume4
Issue number3
DOIs
StatePublished - Sep 2019
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by a grant from the Ministry of Education and Science of Kazakhstan on Science Development program (Agreement N°. 132 of March 12th, 2018).

Publisher Copyright:
© 2019 The Authors

Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.

Keywords

  • Hematite
  • Hollow spheres
  • Morin transition
  • Thermal hysteresis

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