Effect of Zn doping on the tetragonally distorted CuFe2O4 structure

Jolanta Darul 1Waldemar Nowicki 1Dmytro M. Trots 2

1. Adam Mickiewicz University, Faculty of Chemistry, Grunwaldzka 6, Poznań 60-780, Poland
2. Hamburger Synchrotronstrahlungslabor HASYLAB, Notkestrasse 85, Hamburg 22607, Germany

Abstract

Considering the various spinel ferrites, CuFe2O4 has gained a prominent interest among materials science researchers both fundamentally and technologically for various applications. Since of Cu2+ is a Jahn-Teller ion, it gives the anomalous favorable properties and also exhibits phase transition from tetragonal to cubic. The partial diamagnetic substitution of Cu2+ for Zn2+ restrains the Jahn Teller effect - changes of stoichiometry reduce the crystallographic transition temperature.

Polycrystalline zinc-cooper-iron oxides were prepared by a sol-gel method. The compounds formation and crystallinity of the materials were identified by XRD patterns, which were recorded on a Bruker D8 Advance diffractometer, with CuKα radiation.

Effect of substitution with Zn2+ ions in Cu1-xZnxFe2O4 system on its high-temperature structural phase transitions have been investigated on the synchrotron beamline B2 at HASYLAB (DESY, Hamburg). The structure refinement of all polymorphs using Rietveld profile analysis, based on the synchrotron X-ray data, were performed. The cation distribution of Cu1-xZnxFe2O4 samples derived from Rietveld analysis indicates that Cu ions occupy the octahedral B-sites, so tetragonal distortion in these materials is attributed to the cooperative distortion that driven by the octahedral Cu2+ (3d9). As Zn2+ substitutes Cu2+ in these disordered spinels, it replaces Fe3+ at A-site. This is due to the site preference of Zn2+, which leads to transfer Fe3+ from A-sites to B-sites and in turns a crystallographic transformation from tetragonal to cubic structure is occurred. This transformation is attributed to the decrease of the concentration of octahedrally coordinated JT ions  in the host structure and leads to the presence of high-symmetry phase.

 

Acknowledgements: The synchrotron measurements at DESY-HASYLAB were supported by the IA-SFS-Contract No. RII3-CT-2004-506008 of European Commission. We would like to thank Dr. D. Trots  from Hasylab for his assistance during experiments.

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Presentation: Poster at 11th European Powder Diffraction Conference, Poster session, by Jolanta Darul
See On-line Journal of 11th European Powder Diffraction Conference

Submitted: 2008-04-30 18:20
Revised:   2009-06-07 00:48
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