Ferroelectrics, 464:35–41, 2014 Copyright © Taylor & Francis Group, LLC ISSN: 0015-0193 print / 1563-5112 online DOI: 10.1080/00150193.2014.892810 Effect of Variable Valence Ion Doping on the Dielectric Properties of BaTiO 3 –Based Materials W. BAK, 1 P. DULIAN, 2,∗ D. SITKO, 1 B. GARBARZ-GLOS, 1 C. KAJTOCH, 1 K. WIECZOREK-CIUROWA, 2 AND I. SMELTERE 3 1 Institute of Physics, Pedagogical University, Cracow, Poland 2 Faculty of Chemical Engineering and Technology, Cracow University of Technology, Poland 3 Institute of Solid State Physics, University of Latvia, LV-1063 Riga, Latvia Dielectric properties of BaTiO 3 , BaTiO 3 + 0.1 wt.% Fe 2 O 3 and BaTiO 3 + 1 wt.% Fe 2 O 3 ceramics were studied. The dielectric measurements were performed at the temperature ranging from 130 K to 500 K and at the frequency ranging from 0.1 Hz to 10 MHz. Phase transitions were also determined by a thermal analysis in a wide temperature range. Both thermal analysis and electrical characterization techniques show that the temperature of phase transition is shifted towards lower temperatures with increasing Fe 2 O 3 content. The changes and diversity of the observed phase transition temperatures occurred as a consequence of the ion substitution. Such behaviour of the investigated polycrystalline materials may be due to the multivalence nature of the incorporated ions. Keywords BaTiO 3 ; Fe-doped BaTiO 3 ceramics; DSC; phase transition Introduction Most of the ferroelectric oxides e.g. BaTiO 3 (BT) have a great technical value in numerous device applications [1]. The reason for the growing interest are not only the widely known and respected properties in practical applications, but also the ability to change these properties by introducing impurities into the system [2–4]. A doping with transition metal ions has a significant influence on the dielectric and ferroelectric properties of BT. They are used frequently as impurities to improve the electrical properties of the material [1]. BT is an important ferroelectric semiconductor material with a wide band gap of about 3.8 eV and the paraelectric–ferroelectric (PE–FE) phase transition temperature near 400 K [5]. As in the other perovskite ABO 3 ferroelectrics, there is hybridization between Ti-3d and O-2p, which is responsible for the ferroelectricity tendency. At room temperature, pure BT has a tetragonal structure of perovskite type. With rising temperature it changes to a paraelectric cubic phase [1]. In the case of phase transition, a small displacement of Ti 4+ ions leads Received September 2, 2013; in final form October 10, 2013. ∗ Corresponding author. E-mail. E-mail: piotrdulian@indy.chemia.pk.edu.pl [433]/35