CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 39 (2013) 7571–7575 Dielectric properties of Bi-doped Ba 0.8 Sr 0.2 TiO 3 ceramic solid solutions Fathi Bahri * , Hamadi Khemakhem Laboratoire d′Études des Matériaux Multifonctionnels (LÉMM), Unité de Physique-Mathématiques 05UR15-04, Université de Sfax, Faculté des Sciences de Sfax (FSS), Route de Soukra km 3.5, B.P. 1171, 3000 Sfax, Tunisie Received 19 January 2013; received in revised form 1 March 2013; accepted 2 March 2013 Available online 14 March 2013 Abstract Bismuth-doped barium–strontium–titanate ceramics of the formula (Ba 0.8 Sr 0.2 ) (1-1.5y) Bi y TiO 3 were prepared using a conventional solid-state reaction method. The structure, dielectric properties, and ferroelectric relaxor behaviour of all compositions were thoroughly investigated. The findings revealed a broad dielectric anomaly and a shift in dielectric maxima towards higher temperatures with increasing frequency. The diffuseness degree indicator γ was about 1.68, and dielectric relaxation was noted to follow the Vogel–Fulcher relationship, with T f ¼ 185 K, f 0 ¼ 1.18 Â 10 10 Hz, and Ea ¼ 0.35 eV, which further supported the spin-glass-like properties of BBSTs. The latter were also noted to display significant ferroelectric relaxor behaviour that could be attributed to the presence of Bi 3 þ doping ions. The degree of relaxation behaviour was noted to increase with the increase in bismuth concentration. Raman spectra were investigated as a function of temperature, and the findings confirmed the results from X-ray and dielectric measurements. Among the compositions assayed in this solid solution, 10% Bi-doped Ba 0.8 Sr 0.2 TiO 3 yielded promising relaxor properties that make it a strong candidate for future industrial application in the production of efficient and eco-friendly relaxor ferroelectric materials. & 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: C. Dielectric properties; C. Ferroelectric; C. Relaxors; D. Perovskite 1. Introduction Due to their attractive physical properties, such as high dielectric permittivity, diffuse phase transition and strong electrostriction, relaxor ferroelectric materials have attracted special attention during the last few decades. They have been successfully applied in a wide range of systems and technol- ogies, including sensors, actuators, transducers, and memory elements [1–4]. Most of these materials belong to complex lead-based perovskite compounds, such as PMN–PT and PMN–PZT, whose superior dielectric properties and relaxor behaviour have had considerable contributions in the develop- ment of relaxor ferroelectric materials. These materials have, however, often been reported to pose a number of environ- mental and health concerns due to the volatility and toxicity of lead. These disadvantages have motivated the search for new, efficient, and eco-friendly lead-free relaxor materials. Several lead-free materials with perovskite structure, such as BaTiO 3 (BT) and SrTiO 3 [5], have been investigated in terms of their dielectric relaxation, ferroelectric phase transition and electri- cal properties. Lead-free compositions belonging to BaTiO 3 have often been reported to offer special candidate alternatives. In fact, BaTiO 3 presents a model lead-free ferroelectric perovskite-type oxide (ABO 3 ) that displays several poly- morphic phase transitions and is, therefore, used to correlate important dielectric/ferroelectric properties, such as variations in polymorphic phase transition temperatures, permittivity, and dielectric loss with chemical doping and ceramic microstruc- ture. BaTiO 3 -based materials have also been reported to offer a wide range of commercial applications. In several cases involving the disappearance of orthorhombic and tetragonal phases, doped BaTiO 3 also presents a ferroelectric-Tc- paraelectric transition, depending on both the substitution and the compositions [6]. Recently, the quantum paraelectric material SrTiO 3 has attracted considerable attention for showing exceptional dielec- tric and ferroelectric behavior, which is of interest for various technological applications. Due to its high lattice polarizability, SrTiO 3 is very sensitive to doping. The substitution of Sr 2 þ by Pb 2 þ , Ba 2 þ , Ca 2 þ , Cd 2 þ , Mn 2 þ , or Bi 3 þ ions has often been www.elsevier.com/locate/ceramint 0272-8842/$ - see front matter & 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. http://dx.doi.org/10.1016/j.ceramint.2013.03.010 * Corresponding author. Tél.: þ 21653394715; fax: þ21674274437. E-mail address: thiftrriyosr@yahoo.fr (F. Bahri).