Abstract
We report the synthesis of Ca2Fe2O5 nanoparticles by high-energy ball milling and thermal annealing from α-Fe2O3 and CaCO3. Magnetization measurements, Mössbauer and X-ray spectra reveal that annealing at high temperatures leads to better quality samples. Our results indicate nanoparticles produced by 10h high-energy ball milling and thermal annealing for 2h at 1100°C achieve improved stoichiometry and the full weak ferromagnetic signal of Ca2Fe2O5. Samples annealed at lower temperatures show departure from stoichiometry, with a higher occupancy of Fe3+ in octahedral sites, and a reduced magnetization. Thermal relaxation for temperatures in the 700–1100°C range is well represented by a Néel model, assuming a random orientation of the weak ferromagnetic moment of the Ca2Fe2O5 nanoparticles.
Highlights
Perovskite type oxides are promising systems as candidates for the replacement of catalysis containing noble metals in a number of high-temperature oxidation processes [1]
In this paper we report the synthesis of dicalcium ferrite prepared by high energy ball-milling from stoichiometric amounts of the CaCO3 and Fe2O3 precursors, in an air atmosphere, followed by thermal annealing
The grain size decreases with the milling time, while the lattice parameters are slightly different than that found in literature. (The reference ICSD lattice parameters values are presented in the first column of Table 1.) The fractions of the phases change after milling, and this fact may be related to the lost of a fraction of the CaCO3 material
Summary
Perovskite type oxides are promising systems as candidates for the replacement of catalysis containing noble metals in a number of high-temperature oxidation processes [1]. The structure permits the accommodation of a several metal cations of different valences and has an unusual capacity to support a number of different types of defects [2]. Such systems display a wide variety of interesting effects, they are used to test models for simple antiferromagnets through the investigation of many-sublattice antiferromagnets [3]. The structural and magnetic characterization of the resulting powders are investigated and analyzed through X-ray diffraction, magnetization measurements, Mössbauer spectroscopy, and a theoretical model to describe the magnetic behavior
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