Materials Science and Engineering B 176 (2011) 540–547 Contents lists available at ScienceDirect Materials Science and Engineering B journal homepage: www.elsevier.com/locate/mseb Structural, dielectric, magnetic, magnetodielectric and impedance spectroscopic studies of multiferroic BiFeO 3 –BaTiO 3 ceramics Hemant Singh, Amit Kumar, K.L. Yadav ∗ Smart Materials Research Laboratory, Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247667, India article info Article history: Received 10 June 2010 Received in revised form 26 November 2010 Accepted 11 January 2011 Keywords: Dielectric Antiferromagnetic Multiferroic Magnetoelectric Ceramics abstract Polycrystalline (1-x)BiFeO 3 –xBaTiO 3 (x = 0.00, 0.10, 0.20 and 0.30) ceramics have been prepared via mixed oxide route. The effect of BaTiO 3 substitution on the dielectric, ferroelectric and magnetic prop- erties of the BiFeO 3 multiferroic perovskite was studied. From XRD analysis it revealed that BaTiO 3 substitution does not affect the crystal structure of the (1-x)BiFeO 3 –xBaTiO 3 system up to x = 0.30. Improved dielectric properties were observed in the prepared system. An anomaly in the dielectric con- stant (ε) was observed in the vicinity of the antiferromagnetic transition temperature. Experimental results suggest that in the (1-x)BiFeO 3 –xBaTiO 3 system, the increase of BaTiO 3 concentration leads to the effective suppression of the spiral spin structure of BiFeO 3 , resulting in the appearance of net mag- netization. The dependence of dielectric constant and loss tangent on the magnetic field is a evidence of magnetoelectric coupling in (1-x)BiFeO 3 –xBaTiO 3 system. The impedance analysis suggests the presence of a temperature dependent electrical relaxation process in the material, which is almost similar for all the concentrations in the present studies. The electrical conductivity has been observed to increase with rise in temperature showing a typical negative temperature coefficient of the resistance (NTCR) behaviors analogous to a semiconductor and suggests a non-Debye type of electrical relaxation. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Multiferroic materials exhibit ferroelectric/antiferroelectric and ferromagnetic/antiferromagnetic properties in the same phase. These materials may also exhibit magnetoelectric effect by virtue of which electric polarization is induced in the material on application of magnetic field and magnetization is induced on application of electric effect. This is a rare phenomenon since ferroelectricity and ferromagnetism make a mutually exclusive group [1]; still there are a few materials which have attracted lot of researchers. BiFeO 3 is a single-phase magnetoelectric material. This mate- rial is antiferromagnetic and ferroelectric having antiferromagnetic Neel temperature (T N ) ∼350–370 ◦ C [2] and ferroelectric temper- ature (T C ) ∼810–830 ◦ C [3,4]. With respect to the preparation of BiFeO 3 , the synthesis of polycrystalline BiFeO 3 always results in impurity phases due to the kinetics of its formation. Processing BiFeO 3 with other perovskite structured materials, such as PbTiO 3 , BaTiO 3 , and PZT, would prevent the formation of secondary phases [5–7]. Despite being a ferroelectric, saturated ferroelectric hystere- sis loops have not been obtained for bulk materials due to low resistivity [8]. This low electrical resistivity has prevented practical ∗ Corresponding author. Tel.: +91 1332 285744; fax: +91 1332 286662. E-mail address: klyadav35@yahoo.com (K.L. Yadav). application of the material as either a piezoelectric or magneto- electric functional component. The resistivity of BiFeO 3 has been increased by rapid liquid phase sintering [9,10] or by making solid solutions with other perovskite structured materials [5–7] or dop- ing with rare earth elements [11,12]. The inhomogeneous spin structure of BiFeO 3 leads to the cancellation of macroscopic mag- netization which prohibits the linear magnetoelectric effect from being observed [13,14]. This incommensurate spiral spin structure can be suppressed by high magnetic field [15] and by various dop- ings [16]. The resistivity and magnetization are to be increased considerably to find its application in technology. In this paper we report the synthesis of (1-x)BiFeO 3 –xBaTiO 3 ceramics with composition x = 0.00, 0.10, 0.20 and 0.30 and study the effect of BaTiO 3 substitution on structural, dielectric, magnetic, magnetodielectric and electrical properties. Electrical properties have been carried out using complex impedance spectroscopy (CIS) technique, which is a very convenient tool to correlate the struc- tural/microstructural and electrical properties relationship in a polycrystalline ceramics. 2. Experimental Ceramic samples of (1-x)BiFeO 3 –xBaTiO 3 (x = 0.00, 0.10, 0.20 and 0.30) were prepared as a two step process. At first BiFeO 3 was prepared in molten alkali nitrates and then (1-x)BiFeO 3 –xBaTiO 3 0921-5107/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.mseb.2011.01.010