Structure and phase transition in BaThO3: a combined neutron and synchrotron x-ray diffraction study
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Date
2017-12-15
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Publisher
Elsevier
Abstract
The structure of BaThO3, obtained by solid state synthesis, was refined for the first time by the Rietveld method using a combination of synchrotron X-ray and neutron powder diffraction data. BaThO3 has an orthorhombic structure at room temperature, in space group Pbnm with a = 6.3491(5), b = 6.3796(4) and c = 8.9907(7) Å. Heating BaThO3 to above 700 °C results in a continuous transition to a second orthorhombic structure, in space group Ibmm, demonstrated by both in situ neutron and synchrotron X-ray powder diffraction measurements. The coefficient of volumetric thermal expansion for BaThO3 is determined to be 1.04 × 10−5 °C-1 from 50 to 625 °C (Pbnm phase), and 9.43 × 10−6 °C-1 from 800 to 1000 °C (Ibmm phase). BaThO3 was found to decompose upon exposure to atmospheric moisture resulting in the formation of ThO2. The thermal expansion of ThO2, which invariably co-exists with BaThO3, is also described. © 2017 Elsevier B.V.
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Keywords
Phase transformations, Neutron diffraction, X-ray diffraction, Perovskites, Barium, Thorium, Oxides, Thermal expansion
Citation
Murphy, G. L., Kennedy, B. J., Zhang, Z., Avdeev, M., Brand, H. E. A., Kegler, P., & Alekseev, E. V. (2017). Structure and phase transition in BaThO3: a combined neutron and synchrotron x-ray diffraction study. Journal of Alloys and Compounds, 727, 1044-1049. doi:10.1016/j.jallcom.2017.08.200