Please cite this article in press as: B. Senthilkumar, et al., Structural, magnetic, electrical and electrochemical properties of NiFe 2 O 4 synthesized by the molten salt technique. Mater. Chem. Phys. (2011), doi:10.1016/j.matchemphys.2011.06.043 ARTICLE IN PRESS G Model MAC-14997; No. of Pages 8 Materials Chemistry and Physics xxx (2011) xxx–xxx Contents lists available at ScienceDirect Materials Chemistry and Physics j ourna l ho me pag e: www.elsevier.com/locate/matchemphys Structural, magnetic, electrical and electrochemical properties of NiFe 2 O 4 synthesized by the molten salt technique Baskaran Senthilkumar a , Ramakrishnan Kalai Selvan a,∗ , Palanisamy Vinothbabu b , Ilana Perelshtein c , Aharon Gedanken c,∗ a Solid State Ionics and Energy Devices Laboratory, Department of Physics, Bharathiar University, Coimbatore 641 046, India b Department of Physics, Gobi Arts & Science College, Gobichettipalayam 638 453, India c Kanbar Laboratory for Nanomaterials, Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel a r t i c l e i n f o Article history: Received 31 December 2010 Received in revised form 22 June 2011 Accepted 23 June 2011 Keywords: Spinel ferrite Molten salt synthesis Ferrimagnetic Electrical conductivity pseudocapacitance Electro-catalyst a b s t r a c t Submicron-sized NiFe 2 O 4 particles were synthesized by the molten salt method at 900 ◦ C using binary melts of a NaCl and KCl mixture that acts as a flux. The X-ray diffraction pattern confirmed the sin- gle phase, high crystalline and cubic structure of NiFe 2 O 4 with a Fd3m space group. The FT-IR spectra reveal the stretching vibration of octahedral complexes of Fe 3+ –O 2- through the observed band around 552.3 cm -1 . The SEM and TEM image had indicated the formation of submicron-sized NiFe 2 O 4 particles. The ferrimagnetic behavior and high saturation magnetization of 44 emu g -1 was elucidated by VSM. The maximum electrical conductivity of 1.42 × 10 -4 S cm -1 was observed at 873 K. The NiFe 2 O 4 showed a pseudocapacitive property in 1 M of a LiClO 4 electrolyte and exhibited a specific capacitance of 18.5 F g -1 at 10 mV s -1 . The hydrogen evolution reaction was also studied for NiFe 2 O 4 in 1 M of a H 2 SO 4 solution. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Mixed metal oxides having different structures such as spinel (AB 2 O 4 ), perovskite (ABO 3 ), delafossites (ABO 2 ), olivine (ABPO 4 ), magneto-plumbite (AB 12 O 19 ) and garnet (A 3 B 2 (SiO 4 ) 3 ) are used in various applications [1]. Depending upon their crystal structure and cation distribution, the materials exhibit different electrical, mag- netic and electrochemical properties. Oxide spinels are one of the mixed metal oxides, represented by the general molecular formula of AB 2 O 4 , where the A and B are the divalent and trivalent cations. The cations occupy tetrahedral (A) and octahedral (B) interstitial positions of the fcc lattice formed by O 2- ions [2]. Among the vari- ous spinels, ferrites are widely used in different fields due to their crystal structure, magnetic properties, physical flexibility, electri- cal resistivity, and chemical stability [3]. These materials are being used in various fields such as microwave, electromagnetics, spin- tronics, photovoltaics, and gas sensors [4,5]. Recently, the peculiar electrochemical properties of spinel ferrites have been used in var- ious electrochemical devices [6,7]. Among the spinel ferrites, NiFe 2 O 4 possess a fully inverse spinel crystal structure, a ferrimagnetic nature with low magnetic coer- civity, chemical stability, mechanical hardness, and an excellent ∗ Corresponding authors. Tel.: +91 422 2428446; fax: +91 422 2425706. E-mail addresses: selvankram@buc.edu.in (R. Kalai Selvan), gedanken@mail.biu.ac.il (A. Gedanken). electrochemical performance [8]. Recently, NiFe 2 O 4 has been iden- tified as the suitable electrode material in electrochemical devices such as Li-ion batteries as a negative electrode [9] and as superca- pacitors [10]. It is well known that the particle size and shape play a major role that tunes their electrochemical properties [11,12]. Hence, the synthesis procedure is the subject of much interest for the preparation of different nano/microstructures [13]. In this regard, the present work attempts a preliminary study of the syn- thesis of NiFe 2 O 4 for electrodes in supercapacitors by a molten salt method. The molten salt synthesis or flux growth method is one of the simplest methods for preparing pure and stoichiometric pow- ders of multi-component oxides [14]. Moreover, the molten salt synthesis is a simple, low-cost technique, and does not require any organic solvents or surfactants. In this method, the alkali chlorides or fluorides are commonly utilized as solvent or reacting species, or sometimes both [15,16]. The diffusion rates of the components in molten salts are much higher than those in solid-state reactions. Using this novel method, Darshane et al. have prepared ZnFe 2 O 4 nanoparticles at 700 ◦ C using NaCl as a growth inhibitor [17]. Recently, NiFe 2 O 4 nanocrystals were prepared using NiSO 4 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2 O, NaOH and NaCl as starting compounds at 700 ◦ C for petroleum gas sensor applications [18,19]. Other than the molten salt method, NiFe 2 O 4 has been synthesized by a solid-state reaction [20], co-precipitation [21], a sol–gel process [22], a mechanochem- ical reaction [23], and hydrothermal method [24], etc. In the present work, we have prepared submicron-sized NiFe 2 O 4 crystals using NiO and Fe 2 O 3 as starting compounds 0254-0584/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2011.06.043