Appl Phys A (2013) 112:387–395 DOI 10.1007/s00339-012-7412-6 Impedance spectroscopy of Gd-doped BiFeO 3 multiferroics Samita Pattanayak · B.N. Parida · Piyush R. Das · R.N.P. Choudhary Received: 25 July 2012 / Accepted: 29 October 2012 / Published online: 22 November 2012 © Springer-Verlag Berlin Heidelberg 2012 Abstract The polycrystalline Bi 1−x Gd x FeO 3 (BGFO) (x = 0.0, 0.05, 0.10, 0.15, 0.20) materials were synthesized by a solid-state reaction (mixed oxide) technique. Preliminary X-ray structural analysis of the compounds confirmed the formation of single-phase polycrystalline samples. Room temperature scanning electron micrographs of the materi- als revealed the size, type and distribution of grains on the surface of samples. Studies of impedance, electrical modu- lus and electric conductivity of the materials in a wide fre- quency (10–1000 kHz) and temperature (30–500 ◦ C) range using a complex impedance spectroscopy technique have provided considerable vital information on contribution of grains, grain boundary and interface in these parameters. A strong correlation between these electrical parameters and microstructures (bulk, grain boundary, nature of charge car- rier, etc.) of the materials was established. The frequency dependence of electric modulus and impedance of the mate- rial shows the presence of non-Debye type of relaxation. 1 Introduction Although ferromagnetic as well as ferroelectric materials are known for quite a long time for different types of applica- tions, a tremendous interest has been generated recently with discovery of both these properties in a single-phase mate- rial, BiFeO 3 . This has prompted us to design and develop new single-phase materials with high dielectric constant, S. Pattanayak ( ) · B.N. Parida · P.R. Das · R.N.P. Choudhary Department of Physics, Institute of Technical Education & Research, Siksha ‘O’ Anusandhan University, Bhubaneswar 751030, Odisha, India e-mail: samitaphy@gmail.com Fax: +91-674-2351217 low tangent loss, high spontaneous polarization, high mag- netization, small structural distortion and high temperature phase transition for multifunctional applications. Multifer- roics are such type of compounds that possess two or more primary ferroic order parameters such as spontaneous polar- ization, spontaneous magnetization and spontaneous strain. These parameters occur mainly due to the electric, mag- netic and stress fields applied on the materials. During last few decades, some important multiferroic materials, such as YMnO 3 , BiMnO 3 , TbMnO 3 , BiFeO 3 (BFO) etc., were dis- covered with variety of characteristics. Unfortunately, most of these materials have ferroelectric and magnetic phase transitions at very low temperatures and small electric and magnetic polarization with large leakage current, and hence they are not much useful for devices. Among all the multi- ferroic materials known today, BFO has unique properties, namely high ferroelectric (i) and magnetic (ii) phase transi- tions, and (iii) high order parameters that are useful for mul- tifunctional devices. BFO has rhombohedral (and distorted perovskite) structure of a general formula ABO 3 (A = mono or divalent, B = trivalent ions) [1, 2]. The X-ray diffraction study shows that the material has a space group R3c [3]. In the last few years, this material has extensively been stud- ied to (i) enhance its electrical and magnetic properties, (ii) reduce structural distortion, (iii) reduce leakage current, (iv) decrease dielectric loss, and (v) solve some inherent prob- lems. With enhanced properties, the material can be used for multifunctional devices (i.e., spintronics, information stor- age devices, multistate nonvolatile memories, sensors, phase shifters, amplitude modulators, optical wave devices, etc. [4, 5]). Generally, BFO exhibits two types of long range ordering: the ferroelectric ordering below a Curie temper- ature (T c ) of 1100 K and the anti-ferromagnetic ordering below a Neel temperature T N of 643 K [3]. Detailed studies of various properties show some major drawbacks of BFO