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Dresden 2006 – scientific programme

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DF: Dielektrische Festkörper

DF 3: Poster Session

DF 3.25: Poster

Monday, March 27, 2006, 09:30–17:00, P1

Temperature evolution of the phonon anomalies in relaxor ferroelectic PbSc0.5(Nb,Ta)0.5O3 — •Boriana Mihailova1, Ulrich Bismayer1, Bernd Güttler2, Rainer Stosch2, and Marin Gospodinov31Mineralogisch-Petrographisches Institut, Universität Hamburg, Grindelallee 48, D-20146 Hamburg, Germany — 2Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany — 3Institute of Solid State Physics - Bulgarian Academy of Sciences, Blvd. Tzarigradsko Chausee 72, 1784 Sofia, Bulgaria

Single crystals of stoichiometric PbSc0.5Ta0.5O3 (PST) and PbSc0.5Nb0.5O3 (PSN) as well as mixed PbSc0.5(NbxTa1−x)0.5O3 compounds are investigated by Raman scattering and X-ray diffraction. The temperature dependence of the polarized Raman spectra reveals different preferred ferroic species in PST and PSN. Near the dielectric constant maximum cooperative shifts of Pb atoms in respect to the oxygen sheets perpendicular to the cubic body diagonal occur in larger spatial regions for PST than for PSN. On cooling down this structural modification becomes preferential for PST, thus giving rise to highly anisotropic ferroelectric domains. In PSN the temperature decrease favours B-cation deviations from the BO6-octahedral centres, which leads to formation of small-sized polar clusters distributed in the isotropic matrix. Near 180 K PST undergoes an additional phase transition, which involves reduction of the rotation symmetry. The loading of Nb into PST affects strongly the nanoscale domain texture and the structural transformations that occur on cooling down.

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