Temperature dependence of lattice parameters of bismuth sesquioxide (Bi2O3) has been obtained between 26° and 778°C by the Rietveld method using neutron powder diffraction data. Lattice parameters and unit-cell volume of α and phases increased, while the angle of α phase decreased with an increase of temperature. Here the denotes the lattice parameter a of the α phase on the basis of pseudo-fluorite lattice. The thermal expansion coefficients of α phase were 26.7, 6.6, and 9.0 (× 10−6°C−1) for and axes, respectively, indicating a large anisotropy. The α- to - phase transition of Bi2O3 was confirmed between 721° and 760°C on heating. At the α– transition point, the lattice parameters and unit-cell volume discontinuously changed, indicating that the transition is of the first order.
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Document Type: Research Article
Department of Materials Science and Engineering, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama 226-8502, Japan
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
Publication date: 2005-08-01