title: Surfactant-free hydrothermal synthesis of highly tetragonal barium titanate nanowires: a structural investigation.
abstract: Barium titanate nanowires synthesized with a surfactant-free hydrothermal method have been characterized by various techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), synchrotron X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The TEM and SEM analyses show the uniform cylindrical nanowires. The Rietveld refinement with synchrotron X-ray powder diffraction showed that the lattice parameters of cubic and tetragonal phases were a (= b = c) = 4.0134 A and a (= b) = 3.9998 A, c = 4.0303 A, respectively. The final weighted R-factor, R(wp), was 6.75% and the goodness of fit indicator was 1.30. The mass fraction of tetragonal and cubic phases based on the refined scale factor for the two phases were 98.4% and 1.6%, respectively, which clearly show the nanowires are tetragonal. The XPS analysis has shown that as-obtained BaTiO3 nanowires were phase pure. The Raman spectra confirm the tetragonal phase of the BaTiO3 nanowires. The dielectric constant measurement shows the shift in the transition temperature (Tc = 105 degrees C) compared to the bulk transition temperature (Tc = 132 degrees C). The dielectric constant at Tc was 174 measured at 1 kHz frequency.
authors.affiliation: Department of Chemical Engineering and School of Environmental Science and Engineering, Pohang University of Science and Technology, San 31 Hyoja-dong, Pohang 790-784, Korea.
authors.forename: Upendra A
authors.initials: UA
authors.lastname: Joshi
authors.forename: Songhak
authors.initials: S
authors.lastname: Yoon
authors.forename: Sunggi
authors.initials: S
authors.lastname: Baik
authors.forename: Jae Sung
authors.initials: JS
authors.lastname: Lee