IFEG   20353
INSTITUTO DE FISICA ENRIQUE GAVIOLA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Phase evolution and magnetic behavior of mechanochemically activated Fe3O4-La2O3-Y2O3 powder mixtures
Autor/es:
A. CRISTÓBAL; P. BOTTA; P. G. BERCOFF; E. AGLIETTI; H. R. BERTORELLO; J. M. PORTO LÓPEZ
Lugar:
Buenos Aires
Reunión:
Simposio; 15th International Symposium on Metastable, Amorphous and Nanostructured Materials (ISMANAM); 2008
Resumen:
The influence of NdCo substitution on the magnetic properties of
non-stoichiometric strontium hexaferrite nanoparticles
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Rare earth orthoferrites of the general formula LnFeO3
crystallize in the perovskite orthorhombic structure in which the FeO6
octahedra are distorted according to the ionic size of the rare earth, Ln. These oxides find applications in various
areas such as solid oxide fuel cells, sensors, magneto-optic materials and
catalysis [1-3]. Wet-chemical methods (coprecipitation, citrate, sol-gel, etc) are
promising to produce nanoparticles having discrete sizes and narrow size distribution. However, metal alkoxides and organic solvents
are expensive making the process suitable only for small-scale preparations and
exploratory work. In this study we investigate the
mechanochemical activation as a synthesis method for YxLa1-xFeO3,
x £ 0.5. This technique has been applied in the preparation of a wide
variety of nanostructured materials, because of its relative simplicity and
potential to produce metastable phases [4].
Fig. 1-
Saturation magnetization (Ms) and coercivity (Hc) as a function of activation
time.
Fe3O4-La2O3-Y2O3
powder mixtures were mechanically activated in a planetary ball-mill, using
vials and balls made of hardened steel. The physicochemical and microstuctural
evolution of the treated materials was conducted by XRD, VSM and SEM.
XRD reveals the formation of YxLa1-xFeO3
from 1 h of mechanical activation. Peaks corresponding to reactants are no
longer observed after 3h, suggesting the completion of the reaction.
Figure 1
shows the variation of saturation magnetization (Ms) and coercivity (Hc) with
activation time for sample with x=0.5. At short milling times an increase of Hc
is observed, revealing that the decrease of particle size is the main effect of
in the first period of mechanical activation. From 1 h on, both curves confirm
the gradual consumption of Fe3O4 together with the formation of
antiferromagnetic Y0.5La0.5FeO3. However, a ferromagnetic contribution is
observed even after 3 h of milling, which can be attributed to remaining Fe3O4
or to canting in the alignment of the two sub-lattices in orthoferrite structure.
References:
[1]
A. Delmastro et al, Mater. Sci. Eng. B 79 (2001) 140.
[2] N.Q. Mih, J. Am. Ceram. Soc. 76 (1993) 563.
[3] G. Martinelli et al, Sensors Actuators B 55 (1999) 99.
[4] C. Suryanarayana, Prog. Mater. Sci. 46 (2001) 1-184.