Journal of the Korean Physical Society, Vol. 46, No. 1, January 2005, pp. 308∼310 Synthesis and Nanodomain Patterns of BaTiO 3 Nanoparticles Chung-Sik Kim ∗ and Jong-Ho Park † Basic Science Research Institute, Pukyong National University, Busan 608-737 Byung Kee Moon, ‡ Hyo-Jin Seo and Byung-Chun Choi Department of Physics, Pukyong National University, Busan 608-737 Ki-Ho Yeo and Su-Tae Chung Department of Electronic Engineering, Pukyong National University, Busan 608-737 Se-Mo Son Division of Image Science and Information Engineering, Pukyong National University, Busan 608-739 Jong Pil Kim Korea Basic Science Institute, Busan Branch, Busan 609-735 (Received 5 August 2004) Barium titanate (BaTiO3) nanoparticles are synthesized by the solvothermal method. Precursor BaTi(OR)6 was obtained by mixing with Ba(OR)2 and Ti(OR)4 in benzene and aging. Average size of below 20 nm was measured from a TEM image. FWHM in XRD measurements indicates that particles have both cubic phase and tetragonal phase. Dielectric constant measured for pellets fabricated from the product shows a broad peak below 100 ◦ C, which is possibly due to ferroelectric phase transition. Nanometer-sized domains in a HRTEM image were observed in some particles. Parts of domain patterns changed after thermal treatment at 130 ◦ C for 3 min. Phase system and origin of these domains in the particles are discussed. PACS numbers: 61.46, 77.84 Keywords: Barium titanate, Nanocrystalline materials, Ferroelectric materials I. INTRODUCTION Nanocrystal barium titanate (BaTiO 3 ) materials have been attracting interest due to their applications in tech- nical and fundamental research such as gas-sensitive sen- sors, compact high capacitors, thermistors etc . for the former, and lattice dynamics, microstructures, lumines- cence and so forth for the latter [1–5]. BaTiO 3 , especially the tetragonal phase, has excellent dielectric properties, which make it the most important compound used in the composition of ceramic capacitors, especially for the manufacture of multilayer ceramic capacitors (MLCC) [6–8]. A number of investigators have examined the range of processing conditions under which hydrother- mally derived BaTiO 3 may be obtained. In this method, it is synthesized at temperatures < 250 ◦ C, and usually ∗ Present Address is Department of Physics, Pusan National Uni- versity, Busan 609-735 † Present Address is Department of Science Education, Chinju Na- tional University of Education, Jinju 660-750 ‡ E-mail: bkmoon@pknu.ac.kr; Fax: +82-51-611-6357 crystallized in cubic form, depending on particle size. In this study, we synthesize barium titanate nanopar- ticles by the solvothermal method in which anhydrous benzene is used as solvent rather than aqueous solution. The relation of multi-domains observed in the particles with ferroelectricity and critical size of tetragonal to cu- bic phase are discussed [9–11]. II. EXPERIMENT Ba and Ti alkoxide precursor (BaTi(OR) 6 ) solutions were prepared by dissolving equimolar amounts of bar- ium metal (Aldrich, 99 %) and titanium isopropoxide (Aldrich, 97 %) in a mixed solvent of anhydrous benzene (Aldrich, 99.8 %) and anhydrous isopropanol (Aldrich, 99.5 %). The reaction was conducted at 45 ◦ C with stirring with a magnetic stirrer until the barium metal was completely dissolved [12]. The synthesis process of precursor solutions was performed under a nitrogen at- mosphere. Precursors were mixed with benzene at the ratio of 0.5 mole : 1 l. The mixture was stirred with -308-