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Nanosized barium hexaferrite powders obtained by single microemulsion techniques

Tatyana I. Koutzarova 1Svetoslav Kolev 1Korneli Grigorov 1Tomasz Palewski 2Chavdar Ghelev 1Andrzej J. Zaleski 3Ivan Nedkov 1

1. Institute of Electronics, Bulgarian Academy of Sciences (IE-BAS), 72, Tzarigradsko Chaussee, Sofia 1784, Bulgaria
2. 3International Laboratory of High Magnetic Fields and Low Temperatures, Wrocław, Poland
3. Polish Academy of Sciences, Institute of Low Temperature and Structure Research (INTiBS), Okólna 2, Wrocław 50-422, Poland


The present work aims to prepare barium hexaferrite (BaFe12O19) particles by a single microemulsion technique and to study the possibility to control their sizes. One of the advantages of the single microemulsion technique is considerably lower cost compared to the other microemulsion methods. We use a water-in-oil microemulsion system, where cetyltrimethylammonium bromide (CTAB) acts as a cationic surfactant, n-butanol as a co-surfactant, n-hexanol as a continuous oil phase, and an aqueous phase contains FeCl3 and Ba(NO3)2 (with the Ba/Fe ratio was 1/10). The co-precipitation was performed by a concentrated solution of NaOH at pH = 12. The second step of the synthesis includes calcination of the precursor at low temperature (900°C) in air ambient.

Since the technological synthesis conditions posses a significant influence on the chemical, structural and physical properties of the obtained materials, we investigated the relation between the experimental conditions of BaFe12O19 synthesis and their properties. We studied the influence of the stirring time, the water/surfactant ratio (W0) and metallic ions (Ba2+ and Fe3+) concentration on the particle size distribution and crystallinity of BaFe12O19. The correlation among the microstructure, the magneto-crystalline structure, and the magnetic properties of the barium hexaferrite powders thus prepared was examined as well. The microscopy investigations show a narrower grain size distribution and the average particle size is between 115 and 180 nm depending on the synthesis conditions. These sizes are well below the critical mono-domain diameter for barium hexaferrite (460 nm). We also measured the magnetization-versus-magnetic field at 4.2 K and room temperature. The coercive force is 4.3 kOe for the two temperatures. A saturation magnetization value (Ms) of 43 emu/g was obtained from the magnetization curves in high magnetic fields up to 130 kOe. The magnetic properties may be attributed to the mono-domain structure.


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Presentation: Poster at E-MRS Fall Meeting 2007, Acta Materialia Gold Medal Workshop, by Tatyana I. Koutzarova
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-07-17 11:07
Revised:   2009-06-07 00:44