Neutron diffraction study of diffuse scattering in Cu2−δSe superionic compounds
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Date
2011-05-05
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Publisher
Elsevier
Abstract
Crystal structure and short-range order in Cu2-delta Se compounds were studied in superionic and non-superionic phases using high-resolution neutron diffractometer Echidna at ANSTO. In diffraction patterns of beta-Cu-1.98 Se (ordered phase at ambient T), both Bragg peaks and diffuse background change sharply through the beta -> alpha structural phase transition at T = 414K during heating. In case of alpha-Cu1.75Se (disordered superionic phase at ambient T) the changes are monotonic, showing gradual shifts of Bragg peaks and increased intensity of the diffuse background as a function of temperature. On cooling, both compounds undergo a beta -> beta ' transformation. Diffuse scattering in the alpha-phase shows an oscillating dependence on wavevector, with broad peaks centred at Q similar to 3, 5.5 and 8 angstrom(-1). The measurements taken in energy dispersive mode show that the oscillating diffuse background arises from correlated thermal displacements of the ions. Diffuse scattering is higher for compositions close to stoichiometry and increases with temperature. Theoretical calculations show that the increase in diffuse intensity both with temperature and Cu content is related to correlated thermal vibrations of Se and Cu atoms, with Se-Cu(8c, 32f) and Cu(8c)-Cu(8c) correlations being the most important. (C) 2011 Elsevier B.V.
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Keywords
Ionic conductivity, Neutron diffraction, Inorganic compounds, Bragg curve, ANSTO, Diffuse scattering
Citation
Danilkin, S.A., Avdeev, M., Sakuma, T., Macquart, R., Ling, C.D. (2011). Neutron diffraction study of diffuse scattering in Cu2−δSe superionic compounds. Journal of Alloys and Compounds, 509(18), 5460-5465. doi:10.1016/j.jallcom.2011.02.101