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Browsing by Author "Guttler, B."

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    Effect of Ba incorporation on pressure-induced structural changes in the relaxor ferroelectric PbSc0.5Ta0.5O3
    Welsch, A. M.; Maier, B. J.; Engel, J. M.; Mihailova, B.; Angel, R. J.; Paulmann, C.; Gospodinov, M.; Friedrich, A.; Stosch, R.; Guttler, B.; Petrova, D.; Bismayer, U. (American Physical Society, 2009-09-28)
    Pressure-induced structural changes in the canonical relaxor Pb0.78Ba0.22Sc0.5Ta0.5O3 were studied with both in-house and synchrotron single-crystal x-ray diffraction as well as Raman spectroscopy at pressures up to 9.8 GPa. The results reveal that the substitution of Ba for Pb in ABO(3) perovskite-type structures, i.e., the substitution of a two-valent element with an isotropic electron shell for an isovalent element with a stereochemically active lone pair, leads to a "diffuse pressure-induced phase transition," a structural transformation over a broad pressure range, without a well-defined critical pressure point. The smeared phase transition of the average structure results from the existence of local structural deformations in the vicinity of A-positioned Ba cations.
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    Pressure-induced phase transition in PbSc0.5Ta0.5O3 as a model Pb-based perovksite-type relaxor ferroelectric
    Mihailova, B.; Angel, R. J.; Welsch, A. M.; Zhao, J.; Engel, J.; Paulmann, C.; Gospodinov, M.; Ahsbahs, H.; Stosch, R.; Guttler, B.; Bismayer, U. (American Physical Society, 2008-07-04)
    We report pressure-induced structural changes in PbSc0.5Ta0.5O3 studied by single-crystal x-ray diffraction and Raman scattering. The appearance of a soft mode, a change in the volume compressibility, broadening of the diffraction peaks, and suppression of the x-ray diffuse scattering show that a phase transition occurs near p(c)similar to 1.9 GPa. The critical pressure is associated with a decoupling of the displacements of the B site and Pb cations in the existing polar nanoregions, leading to the suppression of B-cation off-center shifts and enhancement of the ferroic distortion in the Pb-O system.