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Persistent URL http://purl.org/net/epubs/work/51165032
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Record Id 51165032
Title The crystal and defect structures of polar KBiNb2O7
Abstract KBiNb2O7 was prepared from RbBiNb2O7 by a sequence of cation exchange reactions which first convert RbBiNb2O7 to LiBiNb2O7, before KBiNb2O7 is formed by a further K-for-Li cation exchange. A combination of neutron, synchrotron X-ray and electron diffraction data reveal that KBiNb2O7 adopts a polar, layered, perovskite structure (space group A11m) in which the BiNb2O7 layers are stacked in a (0, ½, z) arrangement, with the K+ cations located in half of the available 10-coordinate interlayer cation sites. The inversion symmetry of the phase is broken by a large displacement of the Bi3+ cations parallel to the y-axis. HAADF-STEM images reveal that KBiNb2O7 exhibits frequent stacking faults which convert the (0, ½, z) layer stacking to (½, 0, z) stacking and vice versa, essentially switching the x- and y-axes of the material. By fitting the complex diffraction peak shape of the SXRD data collected from KBiNb2O7 it is estimated that each layer has approximately a ~9% chance of being defective - a high level which is attributed to the lack of cooperative NbO6 tilting in the material, which limits the lattice strain associated with each fault.
Organisation ISIS , ISIS-HRPD , STFC
Funding Information National Science Foundation (DMR-2002319); Welch Foundation (Grant E-1457); Somerville College, Oxford, Oxford Ryniker Lloyd scholarship; Diamond Light Source, Oxford/Warwick Solid State Chemistry BAG to probe composition-structure-property relationships in solids (CY25166); STFC, Beam time allocation (RB2000148)
Related Research Object(s): 10.5286/ISIS.E.RB2000148
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Language English (EN)
Type Details URI(s) Local file(s) Year
Journal Article Dalton Trans (2022). doi:10.1039/D1DT04064B 2022