Synthesis of novel Ferrites

Magnetic materials

Ferrites are mostly ferrimagnetic ceramics and most of them contain iron ions. Since their discovery, they received a lot of attention because of their physical properties, which enable them to be utilized as permanent magnets or microwave absorbers. Those properties depend on the structure and composition of the ferrite. The magnetic properties can be altered by iso- or aliovalent substitution of the iron(III) cations.[1-6] By combining various di- to tetravalent cations, different structures can be obtained, which differ in the stacking of different blocks (S-, R- and T-block) along the crystallographic c-axis.[5-9] Those blocks consist of two, three or four hexagonal oxygen layers, respectively. The oxygen anions form various coordination polyhedra. Octahedra are occupied in every block. The S- and T-blocks display occupied tetrahedra and the R-block contains occupied trigonal bipyramids.

We study the impact of substitutions on structure and properties of ferrites and try to synthesize new types of ferrites.

 (c)
Unit cell viewed along [010] [8] (top) and magnetic hysteresis measurements (bottom left) of the V type ferrite with the composition (Ba,Pb)Fe7.1Ti1.9O15 with different orientations of the crystal in the magnetic field, as well as crystal and SEM pictures of BaFe12−xTixO19 [2] (bottom right).

[1] S. Nemrava, D. A. Vinnik, Z. Hu, M. Valldor, C.-Y. Kuo, D. A. Zherebtsov, S. A. Gudkova, C.-T. Chen, L. H. Tjeng, R. Niewa, Inorg. Chem. 2017, 56, 3861.

[2] D. A. Vinnik, D. A. Zherebtsov, L. S. Mashkovtseva, S. Nemrava, N. S. Perov, A. S. Semisalova, I. V. Krivtsov, L. I. Isaenko, G. G. Mikhailov, R. Niewa, Cryst. Growth Des. 2014, 14, 5834.

[3] D. A. Vinnik, D. A. Zherebtsov, L. S. Mashkovtseva, S. Nemrava, A. S. Semisalova, D. M. Galimov, S. A. Gudkova, I. V. Chumanov, L. I. Isaenko, R. Niewa, J. Alloys Compd. 2015, 628, 480.

[4] D. A. Vinnik, D. A. Zherebtsov, L. S. Mashkovtseva, S. Nemrava, A. K. Yakushechkina, A. S. Semisalova, S. A. Gudkova, A. N. Anikeev, N. S. Perov, L. I. Isaenko, R. Niewa, Mater. Chem. Phys. 2015, 115, 99.

[5] L. Shlyk, S. Strobel, T. Schleid, R. Niewa, Z. Krystallogr. 2012, 227, 545.

[6] S. Nemrava, L. Link, Z. Hu, B. Blaschkowski, S.-C. Liao, H.-J. Lin, C.-T. Chen, T.-S. Chan, L. H. Tjeng, R. Niewa, Z. Anorg. Allg. Chem. in press.

[7] F. Haberey, M. Velicescu, Acta Crystallogr. 1974, B30, 1507.

[8] M. Häßner, D. A. Vinnik, R. Niewa, 19. Vortragstagung für Anorganische Chemie der Fachgruppen Wöhler-Vereinigung und Festkörperchemie und Materialforschung/Book of Abstract. Regensburg: 2018.

[9] R. C. Pullar, Prog. Mater. Sci. 2012, 57, 1191.

Rainer Niewa
Prof. Dr. rer. nat.

Rainer Niewa

Professor

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