Structure and Properties of Magnetic Ceramic Nanoparticles
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Structure and Properties of Magnetic Ceramic Nanoparticles Monica Sorescu1, Tianhong Xu1,2 and Lucian Diamandescu3 1
Duquesne University, Department of Physics, Fisher Hall, Pittsburgh, PA 15282-0321, USA
2
FlexEl, LLC, 387 Technology Drive, College Park, MD 20742, USA
3
National Institute for Materials Physics, P.O. Box MG-7, 77125 Bucharest-Magurele, Romania
ABSTRACT Most recently, magnetic ceramic nanoparticles have attracted considerable scientific interest from the basic research point of view and for their prospective use in chemical sensing, catalysis and electrochemical applications. In this paper we report the successful synthesis of xSnO2-(1-x)α-Fe2O3 system by hydrothermal synthesis and that of xZrO2-(1-x)α-Fe2O3 system by mechanochemical activation. The two nanoparticle systems were analyzed side-by-side using X-ray diffraction (XRD) and Mössbauer spectroscopy. The latter technique was used in its complexity, including the determination of the recoilless fraction using our dual absorber method. This was correlated with the onset of new phases in the systems of interest. INTRODUCTION Hematite is one of the most used oxides, with various applications in scientific and industrial fields. It can be used as semiconductor compound [1], magnetic material [2], catalyst [3], and gas sensor [4]. In particular, due to their sensing properties in detection of dangerous gases, much attention has been devoted to the study of semiconducting oxides. Enhanced gas sensing properties are associated with nanostructured semiconducting oxides, due to their high surface areas and activities. Hydrothermal and high-energy ball milling techniques are well-established methods for chemical synthesis of nanostructured or nanocomposite materials in which non-equilibrium phases, extended solid solutions or complex structures can be formed at convenient values of the processing parameters. Recently, the authors have performed several studies on mechanochemical activation of various mixed oxide systems such as: xIn2O3·(1-x)α-Fe2O3 [5, 6], La2O3−α-Fe2O3 [7], xTiO2·(1-x)α-Fe2O3 [8], and xCeO2·(1-x)α-Fe2O3 [9]. In the case of the In2O3−α-Fe2O3 system with the lowest molar concentration of In2O3 (x=0.1), In-doped hematite was formed after 12 h of high-energy ball milling [5, 6]. Simultaneous substitutions between In3+ and Fe3+ into hematite and In2O3 lattices were reported for 0.3≤x≤0.7. In the case of the xTiO2·(1-x)α-Fe2O3 system, Ti-doped hematite was formed at x≤0.3 whereas at 0.5≤x≤0.9 also Fe substitution for Ti sites in the rutile lattice was observed [8]. Similar findings were reported for the systems containing ceria [9]. On the other hand, a single perovskite phase LaFeO3 was synthesized through ball milling of La2O3 and α-Fe2O3 powders in stoichiometric ratios [7]. In this paper we perform a comparative study of the structural and magnetic properties of xSnO2-(1-x)α-Fe2O3 system obtained by hydrothermal synthesis and that of xZrO2-(1-x)α-Fe2O3 system prepared by mechanochemical activation. The study is conducted by XRD and
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