Journal of Alloys and Compounds 477 (2009) 780–784 Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jallcom BiFeO 3 ceramics synthesized by mechanical activation assisted versus conventional solid-state-reaction process: A comparative study Deepam Maurya, Harikishan Thota, Kanwar Singh Nalwa, Ashish Garg ∗ Department of Materials and Metallurgical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India article info Article history: Received 11 July 2008 Received in revised form 24 October 2008 Accepted 24 October 2008 Available online 13 December 2008 Keywords: Multiferroics Ball milling Magnetic properties Thermal analysis abstract Multiferroic bismuth ferrite, BiFeO 3 , was prepared using conventional solid-state-reaction and mechani- cal activation assisted solid-state-reaction method. Room temperature X-ray diffraction patterns for these samples at various stages of processing were collected to analyze the phase evolution. The patterns showed that as compared to the conventionally processed samples, perovskite structured BiFeO 3 phase formation temperature decreases by ∼100 ◦ C in the samples produced by mechanical activation assisted process. Differential thermal analysis (DTA) measurements of both samples show a ferroelectric transition at ∼825 ◦ C, characteristic of ferroelectric BiFeO 3 . Ferroelectric measurements and the leakage measurements reveal that despite the presence of predominantly BiFeO 3 , mechanical activation assisted samples show higher leakage over the conventionally processed samples, attributed to the decreased grain size and higher defect concentration of the mechanical activation assisted samples. Mechanical activation assisted samples also show enhanced magnetization and a clear magnetic transition at ∼375 ◦ C. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Multiferroics are the materials exhibiting spontaneous electric and magnetic ordering in the same phase and offer potential for the development of spintronic devices, dual storage devices and sensors [1]. BiFeO 3 or BFO is one such material in which ferroelec- tricity and antiferromagnetism coexist at room temperature [2,3]. BFO exhibits two types of long-range ordering: the G-type collinear antiferromagnetic ordering below a Néel temperature (T N ) of 643 K and the ferroelectric ordering at 1103K [4,5]. This compound has a rhombohedrally distorted perovskite structure with the space group R3c [6,7]. Recently, epitaxial films [8] or single crystals [9] of BFO have been shown to possess ferroelectric remnant polarization of more than 50 C/cm 2 , fuelling further research to synthesize this mate- rial in polycrystalline phase pure form. Preparation of polycrystalline phase-pure BFO is reported to be difficult because of its narrow temperature range of phase stabiliza- tion. Various impurity phases have been reported to occur, mainly comprising of Bi 2 Fe 4 O 9 , Bi 12 (Bi 0.5 Fe 0.5 )O 19.5 and Bi 25 FeO 40 [10]. Presence of such impurities results in high leakage in the samples, leading to poor ferroelectric behavior. The most common tech- niques developed for the formation of phase-pure polycrystalline ∗ Corresponding author. Tel.: +91 512 2597904. E-mail address: ashishg@iitk.ac.in (A. Garg). BFO samples are: (a) forming solid solution of BFO with other ABO 3 type of perovskites such as BaTiO 3 [11–14], (b) calcination followed by leaching with nitric acid [10], (c) low temperature thermal treat- ment [15], (d) rapid liquid phase sintering of BFO [16–18], and (e) by using rather expensive but ultrapure starting powders of Bi 2 O 3 and Fe 2 O 3 or with slight deficiency of Bi 2 O 3 [19]. Although the mag- nitude of the change in the properties varies, most reports suggest enhanced ferroelectric properties. However, one must note that the shape of ferroelectric hysteresis loop in many reports remains ques- tionable as shown by Scott [20]. Magnetic behavior of the samples was found to be dependent on the presence of any impurities [13], presence of any dopant [18] and mixed valence states of iron [17]. Previously, to overcome the disadvantages of conventional ceramic processing, researchers have employed mechanical acti- vation method for the synthesis of functional ceramic materials having perovskite and layered perovskite-type structures [21–24]. For most of the ceramic materials investigated, the reactivity of starting materials can be improved significantly by mechanical acti- vation, and therefore the necessary calcination for forming the designed ceramic phase is completed either room temperature or at a lowered temperature than that required for conventional solid-state reaction method. In this paper, we present a compar- ative study of the synthesis of BiFeO 3 ceramics synthesized using mechanical activation assisted synthesis versus conventional solid- state reaction method. The samples were characterized using X-ray diffraction (XRD), thermal analysis (DTA/TGA), ferroelectric and magnetic characterization methods. 0925-8388/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2008.10.155