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Stability and range of the type II Bi 1−x W x O 1.5+1.5x solid solution.

Wind, Julia and Kayser, Paula and Zhang, Zhaoming and Radosavljevic Evans, Ivana and Ling, Chris D. (2017) 'Stability and range of the type II Bi 1−x W x O 1.5+1.5x solid solution.', Solid state ionics., 308 . pp. 173-180.


We have established the stability and range of the cubic type II phase of Bi1 − xWxO1.5 + 1.5x using a combination of X-ray diffraction, neutron diffraction and X-ray absorption spectroscopy. Type II is a high temperature modification that can be obtained by quenching/rapid cooling of samples with compositions between x = 0.148 to x = 0.185. Slower cooling rates yield the stable low temperature polymorph, the tetragonal type Ib phase (Bi rich samples), and mixtures of type Ib and Aurivillius phase (W-rich samples). Throughout the entire solid solution range, type II exhibits a (3 + 3) dimensional incommensurate modulation with modulation vectors slightly smaller than 1/3 based on a cubic fluorite type subcell (δ-Bi2O3). The main structural motifs are well-defined tetrahedra of WO6 octahedra in a δ-Bi2O3-matrix, with additional W being incorporated on corners and face centers of the approximate commensurate 3 × 3 × 3 supercell in octahedral coordination, confirmed by XANES analysis of the W L3-edge. Impedance measurements reveal oxide ionic conductivities comparable to those of yttria-stabilised zirconia even after a decrease in ionic conductivity of about half an order of magnitude on thermal cycling due to transition to the tetragonal type Ib phase.

Item Type:Article
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Available under License - Creative Commons Attribution Non-commercial No Derivatives.
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Publisher statement:© 2017 This manuscript version is made available under the CC-BY-NC-ND 4.0 license
Date accepted:21 July 2017
Date deposited:21 August 2017
Date of first online publication:28 July 2017
Date first made open access:28 July 2018

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