Berlin 2008 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 3: Phase Transitions

DF 3.3: Vortrag

Montag, 25. Februar 2008, 11:20–11:40, EB 407

Pressure-induced phase transition in PbSc_0.5Ta_0.5O₃ — Boriana Mihailova¹, Ross J. Angel², •Anna-Maria Welsch¹, Jing Zhao², Jens Engel², Carsten Paulmann¹, Mihail Gospodinov³, Rainer Stosch⁴, Bernd Güttler⁴, and Ulrich Bismayer¹ — ¹Universität Hamburg, Hamburg, Germany — ²Virginia Tech, Blacksburg, USA — ³Institute of Solid State Physics, Sofia, Bulgaria — ⁴PTB Braunschweig, Germany

Relaxors are ferroelectrics with peculiar structural and physical features having various technological applications. The relaxor structural state consists of polar nanoclusters incorporated into a paraelctric matrix. The temperature evolution of polar nanodomains has been extensively analyzed but up to now only few structural studies have been performed under high pressures.PbSc_0.5Ta_0.5O₃ (PST) is a model representative of Pb-based perovskite-type relaxors. High-pressure studies on PST are rather fruitful to give deeper insights on relaxor structure in general, because: (i) PST shows long-range compositional B-site cation ordering of variable degree; (ii) the temperature of dielectric-permitivitty maximum is near 280 K, suggesting well pronounced polar nanoclusters at room temperature. We report on pressure-induced structural transformations in single-crystal PST samples up to 10 GPa. The structural changes were followed by in-house and synchrotron single-crystal X-ray diffraction and Raman scattering. A continuous phase transition was revealed by the appearance of a soft mode, change in the volume compressibility, broadening of the diffraction maxima and suppression of the x-ray diffuse scattering.