Ferroelectric and octahedral tilt twin disorder and the lead-free piezoelectric, sodium potassium niobate system
Date
2012
Authors
Schiemer, Jason
Withers, Raymond
Liu, Yun
Yi, Zhiguo
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Publisher
Academic Press
Abstract
Using electron diffraction, trends in the local structural behaviour of the KxNa1-xNbO3 (KNN x) 'solid solution' system are investigated and interpreted using an order/disorder based theoretical framework. At room temperature, electron diffraction shows a single plane of transverse polarised, diffuse intensity perpendicular to [0 1 0]p (p for parent sub-structure) across the entire phase diagram, indicative of ferroelectric disorder along the [0 1 0]p direction co-existing with long range ferroelectric order along the orthogonal [1 0 0]p and [0 0 1]p directions. An additional characteristic pattern of diffuse scattering is also observed, involving rods of diffuse intensity running along the [1 0 0]p (*) and [0 0 1]p (*) directions of the perovskite sub-structure and indicative of octahedral tilt disorder about the [1 0 0]p and [0 0 1]p axes co-existing with long range ordered octahedral tilting around the [0 1 0]p direction. A possible crystal chemical explanation for the existence of this latter octahedral tilt disorder is explored through bond valence sum calculations. The possible influence of both types of disorder on the previously refined, room temperature space group/s and average crystal structure/s is examined.
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Keywords
Keywords: Bond-valence sum; Co-existing; Diffuse scattering; Ferroelectric order; Lead-Free; Lead-free piezoelectrics; Long range; Octahedral tilting; Order and disorder; Room temperature; Sodium potassium niobate; Space Groups; Structural behaviour; Structured dif Electron diffraction; Ferroelectric; Lead-free; Order and disorder; Structured diffuse scattering
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Source
Journal of Solid State Chemistry
Type
Journal article
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2037-12-31