85 Processing and Application of Ceramics 3 [1-2] (2009) 85–87 * Corresponding author: tel: +370 2 23 66 000 fax: +370 2 23 66 003, e-mail: juras.banys@ff.vu.lt Dielectric investigations of BiFeO 3 ceramics Simonas Greičius 1 , Juras Banys 1,* , Izabela Szafraniak-Wiza 2,3 1 Faculty of Physics, Vilnius University, Sauletekio al. 9, 2040 Vilnius, Lithuania 2 Institute of Material Science and Engineering, Poznan University of Technology, M. Skłodowska-Curie Sq. 5, 60-965 Poznan, Poland 3 Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznan, Poland Received 16 January 2009; received in revised form 27 April 2009; accepted 17 May 2009 Abstract In this paper we present the results from the investigation of the dielectric permittivity of BiFeO 3 ceramics, prepared by mechanochemical synthesis method in a broad frequency and temperature range. The dielectric permittivity is mainly caused by high conductivity, which is suppressed in the frequencies above 1 MHz. The investigated ceramics showed conductivity activation energy E/k = 11280±12 K, and σ 0 = 54161±800 S. The plots of M * revealed conductivity mechanism with τ 0 = 1.12·10 -13 s, and E/k = 9245 K. Keywords: dielectric spectroscopy, multiferroics, activation energy I. Introduction The magnetoelectric multiferroic materials have drawn a signiicant amount of interest during past few years, as the coexistence of ferroelectric and magnet- ic ordering opens the way to a ield of totally new applications, such as multistate memories. Bismuth ferrite [1] (BiFeO 3 , or BFO) is currently the most in- tensively investigated multiferroic material due to its huge advantages: simple chemical formula, high Cu- rie temperature (1083 K) [2] and high Neel tempera- ture (625 K) [3,4]. Reviews of the general study of magnetoelectricity appeared by Schmid in 1994 [5] and more recently by Fiebig [6] and by Eerenstein et al. [7]. Current inter- est in bismuth ferrite was stimulated primarily by paper from Ramesh’s group in 2003 [8], which showed that it had unexpectedly large remnant polarization P r , ifteen times larger than in single crystals, together with very large ferromagnetism of 1.0 Bohr magneton per unit cell. Ironically, both of these claims proved premature. Thus, better single crystals grown in France in 2006-7 had the same polarization as the ilms, suggesting that the large polarization is intrinsic and not due to epitaxi- al strain enhancement [9–13]; and the intrinsic magneti- zation of thin ilms is now known to be near zero [8,14], ca. 0.02 magnetons/cell, rather than 1.0. However, there are not many published papers con- cerning the dielectric spectroscopy of this material. Due to its high conductivity, the real part of the dielectric permittivity can be accurately measured only at high frequencies. The aim of this paper is to measure the di- electric permittivity of BFO and extract the real con- ductivity of the ceramics. II. Experimental The BiFeO 3 nanopowders were prepared by me- chanically triggered room temperature synthesis from commercially available oxides Bi 2 O 3 and Fe 2 O 3 (99% purity from Aldrich) in a SPEX 8000 Mixer Mill. Af- ter 120 h of high energy milling of the oxide pow- ders in stoichiometric ratio only the bismuth ferrite powder has been obtained, which was conirmed by X-ray diffraction. This powder was hot-pressed in or- der to obtain dense ceramics. The more detailed infor- mation about preparation of BiFeO 3 ceramics may be found in paper by Szafraniak [15]. The complex di- electric permittivity ε * = ε’ - i·ε” was measured by a capacitance bridge HP4284A in the frequency range 20 Hz – 1 MHz and temperature range 300–900 K (Fig. 1). Typical dimensions of samples were ≈ 50 mm 2 area and ≈ 1 mm thickness.