Regensburg 2010 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 16: Phase Transitions

DF 16.3: Vortrag

Donnerstag, 25. März 2010, 15:05–15:25, H11

High-pressure structure of Pb-based relaxor ferroelectrics — •Bernd J. Maier1, Ross J. Angel2, William G. Marshall3, Boriana Mihailova1, Carsten Paulmann1, Jens M. Engel4, Marin Gospodinov5, Anna-Maria Welsch1, Dimitrina Petrova5,6, and Ulrich Bismayer11Mineralogisch-Petrographisches Institut, Universität Hamburg — 2Crystallography Laboratory, Virgina Tech, Blacksburg, USA — 3ISIS neutron facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, UK — 4Institut für Werkstoffwissenschaft, Technische Universität Dresden — 5Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia, Bulgaria — 6South-West University “Neofit Rilski”, Blagoevgrad, Bulgaria

The pressure-induced phase transitions that occur in the perovskite-type relaxor ferroelectric PbSc0.5Ta0.5O3 (PST) and Pb0.78Ba0.22Sc0.5Ta0.5O3 (PST-Ba) were studied with combined neutron powder diffraction and single-crystal X-ray diffraction. An increase in the intensities of h,k,l = all odd reflections is observed while the intensity of h,h,h peaks, h=2n+1, does not change with pressure, indicating a glide-plane pseudo-symmetry of the structural distortion along the ⟨111⟩ cubic directions. Rietveld refinement to the neutron powder data shows that the high-pressure phase has either R3c or R3 symmetry, depending on whether the presence of 1:1 octahedral cation ordering is neglected or taken into account, and comprises anti-phase octahedral tilts of type aaa that continuously evolve with pressure.

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