Abstract
The structure of Mn0.5Zn0.5Fe2O4 spinel ferrite nanoparticles is studied as a function of their size and the experimental conditions of their synthesis using X-ray absorption spectroscopy. The nanoparticles of different sizes down to approximately 2 nm and with a narrow size distribution were synthesized using co-precipitation in reverse microemulsions. Simultaneous refinement of the X-ray absorption fine structure (EXAFS) of three constituting metals shows a migration of Mn and Zn ions to the octahedral site of the spinel lattice compensated by the corresponding migration of the Fe ions. To a smaller extent, Mn ions switch the occupation site already in bulk and in larger nanoparticles, while a sporadic migration of Zn is detected only in the nanoparticles with sizes below approximately 5 nm. X-ray absorption near edge structure (XANES) reveals considerable variations in the position of the Mn K edge, suggesting the average Mn valence in the nanoparticles to be higher than 3+. Annealing at 500 °C relaxes the structure of as-synthesized nanoparticles toward the structure of the ceramic bulk standard.
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Acknowledgments
This work was supported by the Slovenian Research Agency, the Ministry of Higher Education, Science and Technology of the Republic of Slovenia within the National Research Program and by DESY and the European Community under Contract RII3-CT-2004-506008 (IA-SFS). Provision of synchrotron radiation facilities by HASYLAB (project II-04-065 EC) is acknowledged. The authors would also like to thank Dr. Aljoša Košak for help with the synthesis of the nanoparticles and E. Welter of HASYLAB for expert advice on beamline operation.
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Makovec, D., Kodre, A., Arčon, I. et al. Structure of manganese zinc ferrite spinel nanoparticles prepared with co-precipitation in reversed microemulsions. J Nanopart Res 11, 1145–1158 (2009). https://doi.org/10.1007/s11051-008-9510-0
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DOI: https://doi.org/10.1007/s11051-008-9510-0