Title: Preparation and characterisation of CaO-Bi₂O₃ complex oxide

Authors: Hiroyuki Nakamura; Takuya Uehara; Yuki Obukuro; Kenji Obata; Shigenori Matsushima; Masao Arai; Kenkichiro Kobayashi

Addresses: Department of Integrated Arts and Science, Kitakyushu National College of Technology, 5-20-1 Shii, Kokuraminami-ku, Kitakyushu, 802-0985, Japan. ' Advanced Course of Materials Science and Chemical Engineering, Kitakyushu National College of Technology, 5-20-1 Shii, Kokuraminami-ku, Kitakyushu, 802-0985, Japan. ' Advanced Course of Materials Science and Chemical Engineering, Kitakyushu National College of Technology, 5-20-1 Shii, Kokuraminami-ku, Kitakyushu, 802-0985, Japan. ' Advanced Course of Materials Science and Chemical Engineering, Kitakyushu National College of Technology, 5-20-1 Shii, Kokuraminami-ku, Kitakyushu, 802-0985, Japan; Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Kitakyushu Science and Research Park, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu, 808-0196, Japan. ' Advanced Course of Materials Science and Chemical Engineering, Kitakyushu National College of Technology, 5-20-1 Shii, Kokuraminami-ku, Kitakyushu, 802-0985, Japan; Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Kitakyushu Science and Research Park, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu, 808-0196, Japan. ' Computational Materials Science Center (CMSC), National Institute of Materials Science (NIMS), 1-1 Namiki, Tsukuba, 305-0044, Japan. ' Department of Materials Science, Shizuoka University, 3-5-1 Johoku, Hamamatsu, 432-8011, Japan

Abstract: Ca₄Bi₆O₁₃ powders prepared from a citric acid complex were characterised by X-ray diffraction, UV-vis diffuse reflectance spectra and specific surface area measurements. In a citric acid complex method, the single phase of Ca₄Bi₆O₁₃ crystal was obtained at 700°C in air. The Ca₄Bi₆O₁₃ powders calcined at 700°C for 12 h had a crystallite size of 68 nm and a specific surface area of 1.05 m²/g. The optical band gap of Ca₄Bi₆O₁₃ was estimated to be 2.82 eV. The type of optical transition was direct and this result was consistent with the prediction by a first-principles energy band calculation. The Ca₄Bi₆O₁₃ powders showed a distinct photocatalytic decomposition of methylene blue under visible light irradiation (a wavelength ≥ 420 nm). The visible light response photocatalysis may be ascribed to the small band gap energy, the direct optical transition, and a fairly wide dispersion of the top of the valence band.

Keywords: Ca4Bi6O13; calcium bismuth oxide; photocatalysts; ab initio calculation; energy band; density of states; photocatalytic activity; nanotechnology; citric acid; band gap energy; direct optical transition; valence band.

DOI: 10.1504/IJNT.2013.050886

International Journal of Nanotechnology, 2013 Vol.10 No.1/2, pp.100 - 107

Published online: 07 Dec 2012 *

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