ISSRNS 2012: Abstracts / Synchrotron Radiation in Natural Science Vol. 11, No 1 – 2 (2012) P 04
STRUCTURAL STUDIES OF MAGNETIC Fe DOPED ZnO NANOFIBERS
A. Baranowska-Korczyc∗, K. Fronc, J.B. Pe lka, K. Sobczak, P. D lu ˙zewski, and D. Elbaum Institute of Physics, Polish Academy of Sciences, al. Lotnik´ow 32/46, PL–02668 Warsaw, Poland
Keywords: electrospinning, ZnO nanofibers, ZnFeO
∗e-mail : akorczyc@ifpan.edu.pl
Although many growth techniques were em- ployed to produce magnetic oxides, electrospun magnetic nanofibers are still novel nanostructures.
Electrospinning is gaining more attention due to its versatility and low cost operation. The room tem- perature ferromagnetic nanofibers were obtained by electrospinning and calcinations in air. Our pre- vious work was aimed to join the extensive stud- ies on these magnetic, electrospun Fe doped ZnO nanofibers [1].
Based on the new data, we discuss structural properties of our nanofibers. The X-ray (XRD) structural characterization was performed using synchrotron radiation at the W1 beamline at DESY- HASYLAB. The data were collected with 2θ scan in the glancing incidence geometry (λ = 1.54056 ˚A).
No clear evidence of the second phase can be con- firmed, as could be expected according to the atomic ratio of Fe to Zn, of about 0.1. This was consistent with previously reported results for similar size of ZnO nanocrystals doped with Co and Mn ions [2, 3].
The low activation energy and relatively fast growth of the crystal allowed a large amount of doped ions to be build-in the ZnO crystals. The activation en- ergy for ZnO crystals growth in our nanofibers was estimated to be about 12 kJ/mol, one order of mag- nitude lower than the value for the bulk ceramics ZnO.
We showed that incorporating iron ions into ZnO did not affect the crystal structure of the host based on Electron Energy Loss Spectroscopy (EELS) anal- ysis. We did not observed any precipitates from the second phase with resolution of about 1.5 nm. The sizes of crystals responsible for magnetic properties, as results of zero field cooled and field cooled mea- surements, were diameters between 3 and 10 nm [1]. It implies that the magnetic signal comes from Fe ions build-in ZnO crystals, because we do not observes other crystals (besides ZnO crystals) in this range of sizes. However, presence of the addi- tional crystals in the ZnO matrix, e.g. Fe2O3, FeO, ZnFe2O4with diameter below 1.5 nm not detectable by XRD and EELS techniques is possible.
Figure 1 : Typical X-ray diffraction patterns of Fe doped ZnO nanofibers: the higher (a) and the lower (b) density of nanofibers.
Acknowledgments: The research was partially sup- ported by the European Union within European Re- gional Development Fund, through Grant Innovative Economy (POIG.01.01.02-00-008/08) and by the Min- istry of Science and Higher Education (Poland) through Grant No. N518 424036.
References
[1] A. Baranowska-Korczyc, A. Reszka, K. Sobczak, B.
Sikora, P. Dziawa, M. Aleszkiewicz, L. K lopotowski, W. Paszkowicz, P. D lu˙zewski, B.J. Kowalski, T.A.
Kowalewski, M. Sawicki, D. Elbaum, K. Fronc,
“Magnetic Fe doped ZnO nanofibers obtained by electrospinning,” J. Sol-Gel Sci. Technol. 61 (2012) 494 – 500.
[2] B.B. Straumal, A.A. Mazilkin, S.G. Protasova, A.A.
Myatiev, P.B. Straumal, B. Baretzky, “Increase of Co solubility with decreasing grain size in ZnO,”
Acta Mater. 56 (2008) 6246 – 6256.
[3] B. Straumal, B. Baretzky, A. Mazilkin, S. Protasova, A. Myatiev, P. Straumal, “Increase of Mn solubility with decreasing grain size in ZnO,” J. Eur. Ceram.
Soc. 29 (2009) 1963 – 1970.
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