Preparation and characterisation of CaO–Bi2O3 complex oxide. (10th December 2012)

• Record Type: Journal Article
• Authors: Nakamura, Hiroyuki; Uehara, Takuya; Obukuro, Yuki; Obata, Kenji; Matsushima, Shigenori; Arai, Masao; Kobayashi, Kenkichiro
• Is Part Of: International journal of nanotechnology. Volume 10:Number 1/2(2013)
• Page Start: 100
• Page End: 107
• Publication Date: 2012-12-10
• Subjects: 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; 620.505
• Languages: English
• ISSNs: 1475-7435

Abstract

Ca4 Bi6 O13 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 Ca4 Bi6 O13 crystal was obtained at 700°C in air. The Ca4 Bi6 O13 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 Ca4 Bi6 O13 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 Ca4 Bi6 O13 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.