Synthesis of barium titanate nanopowder using polymeric precursor method V. Vinothini a , Paramanand Singh b , M. Balasubramanian a, * a Composites Technology Centre, Indian Institute of Technology, Chennai 600036, India b Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Chennai 600036, India Received 30 July 2004; received in revised form 6 September 2004; accepted 18 December 2004 Available online 24 March 2005 Abstract Barium titanate powder was prepared by a polymerized complex method based on the Pechini type reaction route, where barium and titanium ions were polymerized in mixed solution of citric acid, ethylene glycol, to form a transparent resin, which was used as a precursor. Barium titanate powder was formed by heat treating the polymeric precursor in air at 500–900 8C. The thermal decomposition of (Ba, Ti) polymeric precursor was studied by thermal analysis. The crystal structure was investigated by X-ray powder diffractometry and Raman spectroscopy. The particle size and morphology of BaTiO 3 were examined by X-ray diffraction and transmission electron microscopy. Cubic BaTiO 3 with some traces of hexagonal phase was present at 500 8C and tetragonal BaTiO 3 at 600 8C and above. However, Raman spectrum showed a mixture of cubic, tetragonal and hexagonal BaTiO 3 at 500 8C and tetragonal BaTiO 3 at 600 8C and above. X-ray line broadening studies of 900 8C heat-treated powders showed average crystallite size of 20 nm. Agglomerated spherical grains are observed at 600 8C. The sintering behavior and dielectric properties of the nanopowders were also studied. # 2005 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: A. Precursors: organic; C. Dielectric properties; D. Perovskites; D. BaTiO 3 and titanates 1. Introduction The demand for high quality electronic ceramics increases rapidly which have led to greatest sophistication in the processing of these materials in powder synthesis stage and subsequent densification [1]. The bulk property of any material, whether it is a metal, semi conductor or an insulator, changes when the crystallite size reduces from macro to molecular level. Some of the physical properties that change due to this size reduction are (i) lowering of melting point, (ii) decrease of onset sintering temperature, (iii) shift in the luminescence peak towards lower l, (iv) disappearance of ferroelectric and ferromagnetic properties, (v) enhancement of electronic and ionic conductivity [2]. In traditional ceramic processing, the resulting microstructure has a wide grain size distribution, multiple phases and inevitably some degree of porosity. These are due to inhomogenity and impurity incorporation in the powder processing stage. The successful synthesis of barium titanate nanopowder with their unique dielectric properties largely depends on the purity and crystal structure that greatly influences on the properties. Low temperature, wet chemical route offer an exciting possibility for the synthesis of high purity, homogeneous, ultrafine and multicomponent pow- ders from which electronic components with tailored and predictable properties could be prepared [1]. In co-precipitation and hydrothermal methods, stoichio- metry deviations and formation of biphasic solid solutions have been reported [3]. Also the high temperature required for achieving complete solid solution in some of the low temperature methods such as sol–gel and metallo-organic decomposition makes them less favourable. Many of these problems can be overcome by using low temperature polymeric precursor method. The advantage of this technique is the quasi-atomic dispersion of constituent components, which facilitates synthesis of the crystallised powder with ultrafine particle size and high purity at low www.elsevier.com/locate/ceramint Ceramics International 32 (2006) 99–103 * Corresponding author. Fax: +91 44 2257 0039. E-mail address: mbala@iitm.ac.in (M. Balasubramanian). 0272-8842/$30.00 # 2005 Elsevier Ltd and Techna Group S.r.l. All rights reserved. doi:10.1016/j.ceramint.2004.12.012