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Powder x-ray scans of KNN18 (a) and KNN30 (b), with zoomed-in regions showing the oxygen octahedral tilt peaks, labeled on a doubled unit cell . Peaks with type odd-even-odd are plus tilts, and odd-odd-odd are minus tilts.
Reconstructed reciprocal lattice images of (a) and (b) plane for KNN20. The red circles show examples of plus tilts, while the blue circles highlight some of the minus tilts.
Change in lattice parameter as a function of temperature for KNN18.
FWHM of the 200/002 “doublet” across the region, showing the transition from doublet to singlet at .
Updated phase diagram for KNN, showing oxygen tilting (superscripts) and cation displacements (subscripts) for each phase [notation taken from Stokes et al. (Ref. 23]. Dotted lines represent change in tilt system, and phases and correspond to phases in Ahtee and Glazer (Ref. 14), but with updated space groups corresponding to the oxygen tilt and cation displacements observed.
Samples used to create phase diagram.
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