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Mechanochemically assisted synthesis of yttrium-lanthanum orthoferrite: Structural and magnetic characterization A.A. Cristóbal a,1, P.M. Botta a,2, P.G. Bercoff b,3, E.F. Aglietti c,4, H.R. Bertorello b,5 and J.M. Porto López a,6 a INTEMA (CONICET-UNMdP) J B Justo 4302 (B7608FDQ) Mar del Plata, Argentina b FaMAF (UNC), Ciudad Universitaria (5000) Córdoba, Argentina. CONICET c CETMIC (CIC-CONICET), C. Centenario y 506 (B1897ZCA) Gonnet, Argentina 1 acristobal@fi.mdp.edu.ar, 2 pbotta@fi.mdp.edu.ar, 3 bercoff@famaf.unc.edu.ar, 4 eaglietti@cetmic.unlp.edu.ar, 5 berto@famaf.unc.edu.ar, 6 jmplopez@fi.mdp.edu.ar 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.