Synthesis of platelets BisFeo.sCoo.s Ti301S via the molten salt method Meghdad Palizdar \ Timothy Comyn\ Santosh Kulkami 2 , Lynette Keenel Saibal Rol, Martyn Pemble 2 , Roger Whatmore 2 , ,Andrew Bell I 1- Institute for Materials Reaserch, University of Leeds, LS2 9JT, LEEDS, UK 2-Tyndall National Institute, 'Lee Maltings', Cork, Ireland MI07m2@leeds.ac.uk Abstract- Oxide materials which exhibit both ferroelectricity and ferromagnetism are of great interest. Layered bismuth titanates with a Aurivillius structure, (BiFe03)n Bi4 Ti3012, can potentially posses ferroelectric and ferromagnetic order paramaters simultaneously. It has recently been demonstrated that one such exampIe, BisFeo.sCoo.sTi30,s where n = 1 with half the Fe 3 + sites substituted by C0 3 + ions exhibits both ferroelectric and ferromagnetic properties at room temperature. Here we report on the fabrication of well oriented polycrystalline ceramics of this material, via molten salt synthesis and uniaxial pressing of high aspect ratio platelets. Electron backscatter images showed that there is an extra secondary phase within the obtained ceramic which is rich in cobalt and iron. The concentration of the secondary phase obtained from secondary electron microscopy is estimated at less than 2.5 %, below the detection limit of XRD. Further, the sintering temperature was varied and excess addition of bismuth oxide was employed in an attempt to reduce the secondary phase with limited success. The samples have been characterized by X-ray diffraction, polarization-ield measurements and SQUID magnetometery as a function of sample orientation. It is inferred from the data that the resultant ferromagnetic response identiied using SQUID measurements is due to the presence of the secondary phase. Keywords-coponent; mut/erroic, txture, microstructure I. INTRODUCTION Aurivillius described compounds, with the general fomula A m + l Biz Mm 0 3m + 3, which have a layered perovskite-like structure where A can be replaced with ions of twelve-fold coordination and B is a combination of ions for octahedrally coordinated sites. E ach perovskite layer ( [Am + lBm03m + 3r 2 ) is sandwiched between (Bi202) 2 + layers. [1]. Bi5Ti3FeOI5, Bi6 Ti3Fe2018 and Bi9 Ti3Fe5027 were reported by Ismailzade which were prepared rom 1 mole Bi4Ti3012 and n mole BiFe03. [2] Bi4 Ti3012 has a crystal structure consisting of altenating layers of pseudo-perovskite (Bi2Ti302 f and 978-1-4244-8191-0110/$26.00 ©2010 IEEE (Bi202) 2 + blocks and changes rom a tetragonal structure at high temperatures to a ferroelectric phase on cooling hrough a temperature of � 67SDC.[3] BiFe03 is an interesting lead-ree material possessing both ferroelectric and antiferromagnetic properties. The structure, which has a rhombohedral symmetry at room temperature, has a spontneous polarization due to bismuth on the A-site and magnetization because of the iron on the B-site.[4] (BiFe03)n Bi4Ti3012 compounds show feroelectric and magnetic ordering simultaneously [S]. In this present work, molten salt synthesis method has been employed to produce Bi5Feo sCoo 5Ti3015 (BFCT) in which half Fe 3 + sites have been replaced by C0 3 + ions. II. EXPERIMENTAL The molten salt method was employed to synthesize platelets of Bi5FeosCoo. 5Ti3015 (BFCT). Using this method, the rate of difusion is much higher in comparison with the solid state reaction, which consequently lead to the signiicant reductions in the powder sintering times and temperatures.[6] The constituent oxide powders, Biz03, Ti02, Fe203 and C0203 (purity, 99.9%, Alrich, Germany) were mixed in stoichiometric quantities with respect to the Bi5FeosCoo .5Ti3015 by ball milling with zirconia balls in iso-propanol for 24 hours. Ater drying, the powders were ground hrough a 100 mesh sieve to reduce aggregate formation. The mixture was added with an equal weight of 1:1 mole ratio NaCI:KCI using an agate pestle and mortar. Then the mixture was placed into an alumina crucible and heated to 1000 DC at a rate of 300 DC h( l , with a 1 hour dwell at temperature, then cooled at a rate of ISO °C hr- 1 to room temperature. The products were crushed and repeatedly washed with hot de-ionized water to remove the salts rom the mixture.