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Please use this identifier to cite or link to this item: http://apo.ansto.gov.au/dspace/handle/10238/3942

Title: Phase diagram, chemical stability and physical properties of the solid-solution Ba(4)Nb(2-x)Ta(x)O(9)
Authors: Dunstan, MT
Southon, PD
Kepert, CJ
Hester, J
Kimpton, JA
Ling, CD
Keywords: Perovskite
Phase Diagrams
Hydration
Diffusion
Ionic Conductivity
Barium Oxides
Issue Date: 1-Oct-2011
Publisher: Academic Press INC Elsevier
Citation: Dunstan, M.T., Southon, P.D., Kepert, C.J., Hester, J., Kimpton, J.A., Ling, C.D. (2011). Phase diagram, chemical stability and physical properties of the solid-solution Ba(4)Nb(2-x)Ta(x)O(9). Journal of Solid State Chemistry, 184(10), 2648-2654.
Abstract: Through the construction of the Ba4Nb2−xTaxO9 phase diagram, it was discovered that the unique high-temperature γ phase is a thermodynamic intermediate between the low-temperature α phase (Sr4Ru2O9-type) and a 6H-perovskite. Refined site occupancies for the γ phase across the Ba4Nb2−xTaxO9 solid-solution indicate that Nb preferentially occupies the tetrahedral sites over the octahedral sites in the structure. When annealed in a CO2-rich atmosphere, all of the phases studied absorb large amounts of CO2 at high temperatures between ∼ 700 and 1300 K. In situ controlled-atmosphere diffraction studies show that this behaviour is linked to the formation of BaCO3 on the surface of the material, accompanied by a Ba5(Nb,Ta)4O15 impurity phase. In situ diffraction in humid atmospheres also confirms that these materials hydrate below ∼ 1273 K , and that this plays a critical role in the various reconstructive phase transitions as well as giving rise to proton conduction.(C) 2011 Elsevier Inc. All rights reserved.
URI: http://dx.doi.org/10.1016/j.jssc.2011.07.036
http://apo.ansto.gov.au/dspace/handle/10238/3942
ISSN: 0022-4596
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