ISSN 1063-7834, Physics of the Solid State, 2006, Vol. 48, No. 6, pp. 1043–1045. © Pleiades Publishing, Inc., 2006. Original Russian Text © O.N. Ivanov, E.A. Skripchenko, A.P. Chumakov, 2006, published in Fizika Tverdogo Tela, 2006, Vol. 48, No. 6, pp. 981–983. 1043 1. INTRODUCTION Ferroelectric magnets combining simultaneously the properties of ferroelectrics (antiferroelectrics) and ferromagnets (antiferromagnets) are traditionally among the most interesting subjects of investigation in solid-state physics [1]. The continuous interest in ferro- electric magnets stems primarily from the possible interrelation of the electrical and magnetic subsystems in these compounds. This interrelation can lead to a number of unique physical effects (for example, the magnetoelectric effect). The SrBi 3 Nb 2 FeO 12 compound was first synthesized by Srinivas et al. [2, 3] and is a new and poorly studied representative of the class of ferroelectric magnets. According to [2, 3], the com- pound has a layered (three-layer) perovskite-like struc- ture that can be considered to consist of the layered (two-layer) ferroelectric SrBi 2 Nb 2 O 9 and the ferroelec- tric magnet BiFeO 3 . One would expect the SrBi 3 Nb 2 FeO 12 compound to undergo phase transitions (both structural ferroelectric and magnetic ones) in the temperature range of existence of the solid phase. The aim of this work is to reveal and study phase transitions in the ceramic SrBi 3 Nb 2 FeO 12 compound by analyzing the temperature evolution of the structure- sensitive dielectric, elastic, and inelastic properties. 2. SAMPLE PREPARATION AND EXPERIMENTAL TECHNIQUES The ceramic SrBi 3 Nb 2 FeO 12 compound was synthe- sized from a mixture of Bi 2 O 3 , Fe 2 O 3 , Nb 2 O 5 , and SrCO 3 powders taken in the stoichiometric ratio using the technique proposed in [2]. This technique is based on successive sintering in air at 1173, 1223, 1273, 1323, and 1373 K. The duration of sintering at each stage was 2 h. After each stage, an intermediate remill- ing was performed. X-ray diffraction analysis using a DRON-4.0 diffractometer (CuK α radiation) confirmed that the synthesized material is indeed the SrBi 3 Nb 2 FeO 12 compound and that there are no traces of other phases. We studied the dielectric properties (the permittivity ε and dielectric loss ) using an E7-12 automatic bridge at a frequency of 1 MHz for samples in the form of plates ~75 mm 2 in area and ~1 mm thick electroded with silver paste. The elastic (shear modulus G) and inelastic (internal friction Q –1 ) properties were studied using a device based on an inverse torsion pendulum [4] at a frequency of ~10 Hz and a strain amplitude of ~10 -4 . The samples under study were in the form of rectangular bars 20 × 2 × 2 mm in size. All the experiments were car- ried out in the temperature range 300–900 K in the con- tinuous-heating mode at a rate of ~1 K/min. 3. EXPERIMENTAL RESULTS AND DISCUSSION By studying the temperature evolution of the dielec- tric properties of a SrBi 3 Nb 2 FeO 12 sample near a tem- perature of ~700 K, we revealed anomalous variations in the permittivity and dielectric loss (Fig. 1). For example, the temperature dependence of ε exhibits a clearly defined asymmetric peak with a maximum value ε max ≈ 325; the peak in ε is matched by a stepwise change in the temperature dependence of . As a rule, the presence of a peak in the ε(T) dependence is characteristic of a ferroelectric phase transition and the temperature corresponding to ε max is the ferroelectric Curie temperature. Therefore, one can suppose that the δ tan δ tan Synthesis and Physical Properties of the Ferroelectric Magnet SrBi 3 Nb 2 FeO 12 O. N. Ivanov, E. A. Skripchenko, and A. P. Chumakov Voronezh State Technical University, Moskovskiœ pr. 14, Voronezh, 394026 Russia e-mail: olniv@mail.ru, katrin_skriptch@mail.ru, chumakov8a@mail.ru Abstract—The dielectric, elastic, and inelastic properties of a ceramic ferroelectric SrBi 3 Nb 2 FeO 12 are studied over the temperature range 300–900 K. The observed anomalies in the temperature dependences of the permit- tivity, dielectric loss, shear modulus, and internal friction indicate the occurrence of a structural phase transition in the compound at ~700 K. It is suggested that the transition is a proper ferroelectric and improper ferroelastic second-order phase transition. PACS numbers: 77.84.Dy, 77.22.Ch, 77.22.Gm DOI: 10.1134/S1063783406060084 PHYSICAL PROPERTIES OF FERROELECTRICS