Journal of the Korean Physical Society, Vol. 46, No. 1, January 2005, pp. 308310
Synthesis and Nanodomain Patterns of BaTiO3 Nanoparticles
Chung-Sik Kim and Jong-Ho Parky
Basic Science Research Institute, Pukyong National University, Busan 608-737
Byung Kee Moon,z 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
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 (BaTiO3) materials have been attracting interest due to their applications in technical and fundamental research such as gas-sensitive sensors, compact high capacitors, thermistors etc. for the former, and lattice dynamics, microstructures, luminescence
and so forth for the latter [1{5]. BaTiO3, 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 hydrothermally derived BaTiO3 may be obtained. In this method, it is synthesized at temperatures < 250 C, and usually crystallized in cubic form, depending on particle size. In this study, we synthesize barium titanate nanoparticles 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 cubic
phase are discussed
II. EXPERIMENT
Ba and Ti alkoxide precursor (BaTi(OR)6) solutions were prepared by dissolving equimolar amounts of barium 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 atmosphere. Precursors were mixed with benzene at the ratio of 0.5 mole : 1 l.
Synthesis and Nanodomain Patterns of BaTiO3 Nanoparticles
