Long- and short-range structure studies of KBT-KBZ solid-solutions using synchrotron radiation

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Royal Society of Chemistry
The relaxor ferroelectric K0.5Bi0.5TiO3 has been synthesised in a solid-solution series with K0.5Bi0.5ZrO3, as K0.5Bi0.5Ti1−xZrxO3. High-resolution synchrotron X-ray powder diffraction and X-ray absorption near edge structure spectroscopy were used to characterise the long-range average and local structural behaviour. Rietveld refinements against diffraction data show that a pseudocubic tetragonal region exists across the whole solid-solution series, with truly cubic symmetry only observed at x = 1 (pure KBZ). Variable-temperature diffraction data for x = 0 (pure KBT) showed a broad ferroelectric transition from tetragonal to cubic symmetry at approximately 683 K with a coexistence of both phases close to that temperature, accompanied by a marked volume contraction. Ti K-edge data showed that Zr doping has a minimal effect on Ti off-centering, and revealed no evidence for local clustering. Metal L-edges showed that Ti4+ cations remain off-centered with increasing Zr content, while Zr4+ cations approach a higher-symmetry coordination environment, most likely due to the increased size of the Zr atoms. Although there is a minimal effect on actual Ti-offsets, an effective dilution of these environments by Zr doping leads to a reduction in polar domains and a diminished ferroelectric response. © 2015 Royal Society of Chemistry
X-ray diffraction, Order-disorder transformations, Crystal-phase transformations, Powders, Ferrimagnetic materials, Absorption, Perovskites, ADP
Liu, S., Blanchard, P. E., Zhang, Z., Kennedy, B. J., & Ling, C. D. (2015). Long-and short-range structure studies of KBT-KBZ solid-solutions using synchrotron radiation. Dalton Transactions, 44(23), 10681-10688. doi:10.1039/C4DT03866E