Dielectric and pyroelectric response of PVDF loaded with BaTiO 3 obtained by mechanosynthesis J. Kulek, I. Szafraniak, B. Hilczer * , M. Polomska Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznan ´ , Poland Available online 1 October 2007 Abstract Electroactive composites based on ferroelectric ceramic and polymer components are still of interest since their properties can be eas- ily tailored to the requirements of smart structures, sensors and actuators. We studied the dielectric and pyroelectric response of poly(vinylidene fluoride) loaded with BaTiO 3 nanograins obtained by mechanically activated synthesis from BaO and TiO 2 . The BaTiO 3 nanopowder was characterized by X-ray diffraction, transmission electron microscopy and NIR Raman scattering. The relaxation pro- cesses in the polymer matrix were found to determine the dielectric response of the composites but with higher permittivity values due to the presence of BaTiO 3 . The activation energy of the segmental motion of the polymer matrix was found to increase with increasing contents of the filler. The dielectric response of the composites with volumetric fraction of BaTiO 3 equal to and greater than 0.24 was found to be dominated by a broad maximum at 320 K, which we relate to the Curie point of the ferroelectric nanograins. Ó 2007 Elsevier B.V. All rights reserved. PACS: 77.84.Lf; 77.84.s; 77.22.Gm; 77.70.+a; 77.80.Bh; 77.84.Dy Keywords: Ceramics; Sensors; Dielectric properties, relaxation, electric modulus; Ferroelectric; TEM/STEM; Powders; Nanocomposites; Nanoparticles; Titanates; Polymers and organics; Long-range order; Short-range order 1. Introduction Many-phase systems containing at least one phase with constituents of less than 100 nm in size are usually termed nanocomposites [1]. Electroactive nanocomposites of 0–3 type connectivity, consisting of polymer matrix loaded with nanograins of electroactive ceramics, have recently attracted a considerable interest due to enhanced sensing and controlling properties for application in smart struc- tures, sensors and actuators. The properties of the compos- ites can be tailored to various requirements by combining the excellent dielectric, piezoelectric and pyroelectric activ- ity of the ceramic and the low permittivity and density of the polymer to obtain materials with low acoustic imped- ance and low dielectric permittivity and losses [2,3]. The temperature and frequency variation of the dielectric per- mittivity e * (T, f) of the composites is essential for determi- nation of the temperature and frequency operation range of electromechanical transducers and pyroelectric sensors because e * is involved in the Figures of Merits. Poly(vinylidene fluoride) (PVDF) and its copolymers loaded with BaTiO 3 (BT) have been studied rather rarely [2,4–8] and the attention was directed mainly to establish the mixing rules of the dielectric, piezo- and pyroelectric activity of the composites. The dielectric permittivity was studied either as dependent on the frequency at room tem- perature or temperature variation of the permittivity was studied at 1 kHz only [5–7]. Recent studies of the dielectric response of (BT) x (PVDF) 1x nanocomposites (with 20– 30 nm BT nanograins obtained by nonisothermal decom- position of barium titanyl oxalate) have shown that though the response is determined by the relaxation processes in the PVDF matrix a contribution of the BT Curie point anomaly is apparent at 320 K in composites with 0022-3093/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2007.02.077 * Corresponding author. Tel.: +48 61 8695140; fax: +48 61 8684524. E-mail address: bhilczer@ifmpan.poznan.pl (B. Hilczer). www.elsevier.com/locate/jnoncrysol Available online at www.sciencedirect.com Journal of Non-Crystalline Solids 353 (2007) 4448–4452