CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 41 (2015) 6912–6919 Effect of Ba–Nb co-doping on the structural, dielectric, magnetic and ferroelectric properties of BiFeO 3 nanoparticles Sanjay Godara, Binay Kumar n Crystal Lab, Department of Physics & Astrophysics, University of Delhi, Delhi 7, India Received 16 January 2015; received in revised form 27 January 2015; accepted 28 January 2015 Available online 4 February 2015 Abstract Multiferroic BFO nanoparticles of compositions Bi 1 x Ba x FeO 3 and Bi 1 x Ba x Fe 1 x Nb x O 3 (x ¼ .05 and .1) have been synthesized using sol–gel followed by an auto-combustion route. The effect of Ba–Nb co-doping on structural, magnetic, dielectric, leakage current and ferroelectric properties has been investigated. XRD patterns confirm the rhombohedral phase for all the samples in which traces of pseudo-cubic phase have been observed as a result of co-doping. The residual and saturation magnetization get increased significantly, which is attributed to a decreased degree of structural distortion and smaller particle size due to co-doping. Dielectric studies show strong dispersion for Ba-doped samples while Ba–Nb co-doped samples are nearly frequency independent. Furthermore, dielectric constant (ε 1 ) at higher frequencies increases with doping level whereas dielectric loss decreases due to reduction in defect centers by co-doping. Temperature dependent dielectric analysis reveals strong anomaly near magnetic transition (T N ), signifying magnetoelectric coupling for all the samples. Leakage current has been decreased to 2–3 orders of magnitude and conductivity behavior has come close to ohmic type for 10% Ba–Nb co-doped sample, which suggested a significant reduction in oxygen vacancies. The saturation level of ferroelectric loop is also improved with doping level and remnant polarization increases from 1.28 μC/cm 2 for 5% Ba-doped to 3.24 μC/cm 2 for 10% Ba–Nb co-doped sample. Hence, Ba and Nb co-doped BFO nanoparticles can be used as a promising candidate for magneto-electric applications. & 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: A. Sol–gel processes; C. Dielectric properties; C. Magnetic properties; D. BFO nanoparticles 1. Introduction Recently, multiferroic materials have attracted considerable rese- arch interests due to their distinguished properties and potential applications in various fields including compact and non-volatile storage devices, spintronics and electro-magnetic sensors [1–6]. The multiferroic materials exhibit two or more ferroic orderings simultaneously, such as ferroelectricity, (anti)ferromagnetism and ferroelasticity. Further, mutual coupling between these order parameters enhances degree of freedom of device applicability. However, these materials are not found in abundance, as mechan- ism responsible for origin of electric and magnetic dipole orderings at microscopic level differs completely in nature [2]. In this respect, bismuth ferrite (BiFeO 3 ; BFO) is the only signi ficant single phase magnetoelectric multiferroics material that possesses ferroelectric (T C ¼ 825 1C) and G-type antiferromagnetic ( T N ¼ 370 1C) order parameters simultaneously well above room temperature [4]. It is an ABO 3 -type perovskite oxide offering rhombohedral symmetry with space group R3c. Despite being a promising multiferroic candidate, there are several concerns related to BFO e.g. compositional instability, higher leakage current, low remnant magnetization (M r ) and high coercive field (E C ), which have to be resolved before its real-world applications. Formation of phase pure BFO by the conventional solid state reaction method is a very challenging task, as its perovskite phase could stabilize only in a very narrow range of temperatures and a slight variation from it leads to additional phases [7]. Additionally, bismuth loss during synthesis processes generates oxygen vacancies and valence fluctuation of Fe atoms, which are the leading cause for high leakage current [8]. BFO is a type-I multiferroic in which magnetic and electric orderings are believed to be resulting from different ionic sites, www.elsevier.com/locate/ceramint http://dx.doi.org/10.1016/j.ceramint.2015.01.145 0272-8842/& 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved. n Corresponding author. Mobile: þ 91 9818168001; fax: þ91 11 27667061. E-mail address: b3kumar69@yahoo.co.in (B. Kumar).