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|Title:||Phase diagram, chemical stability and physical properties of the solid-solution Ba(4)Nb(2-x)Ta(x)O(9)|
|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. doi:10.1016/j.jssc.2011.07.036|
|Abstract:||Through the construction of the Ba4Nb2âˆ’xTaxO9 phase diagram, it was discovered that the unique high-temperature Î³ phase is a thermodynamic intermediate between the low-temperature Î± phase (Sr4Ru2O9-type) and a 6H-perovskite. Refined site occupancies for the Î³ phase across the Ba4Nb2âˆ’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 âˆ¼ 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 âˆ¼ 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.|
|Gov't Doc #:||3806|
|Appears in Collections:||Journal Articles|
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