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

Wind, Julia; Kayser, Paula; Zhang, Zhaoming; Radosavljevic Evans, Ivana; Ling, Chris D.

Abstract

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.

Citation

Wind, J., Kayser, P., Zhang, Z., Radosavljevic Evans, I., & Ling, C. 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, 173-180. https://doi.org/10.1016/j.ssi.2017.07.015

• Journal Article Type: Article
• Acceptance Date: Jul 21, 2017
• Online Publication Date: Jul 28, 2017
• Publication Date: Oct 1, 2017
• Deposit Date: Aug 21, 2017
• Publicly Available Date: Jul 28, 2018
• Journal: Solid State Ionics
• Print ISSN: 0167-2738
• Electronic ISSN: 1872-7689
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 308
• Pages: 173-180
• DOI: https://doi.org/10.1016/j.ssi.2017.07.015
• Public URL: https://durham-repository.worktribe.com/output/1351686