High-temperature structural transformations in the relaxor ferroelectrics PbSc{sub 0.5}Ta{sub 0.5}O{sub 3} and Pb{sub 0.78}Ba{sub 0.22}Sc{sub 0.5}Ta{sub 0.5}O{sub 3}

Journal Article · Thu May 01 00:00:00 EDT 2008 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.77.174106· OSTI ID:21143536

Mihailova, B; Maier, B; Paulmann, C; Malcherek, T; Bismayer, U ^[1]; Ihringer, J ^[2]; Gospodinov, M ^[3]; Stosch, R; Guettler, B ^[4]

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1. Mineralogisch-Petrographisches Institut, Universitaet Hamburg, Grindelallee 48, D-20146 Hamburg (Germany)
2. Institut fuer Angewandte Physik, Universitaet Tuebingen, Auf der Morgenstelle 10, 72076 Tuebingen (Germany)
3. Institute of Solid State Physics, Bulgarian Academy of Sciences, Boulevard Tzarigradsko Chausse 72, 1784 Sofia (Bulgaria)
4. Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany)

Temperature-driven structural transformations in Pb-based perovskite-type relaxors are studied by using polarized Raman spectroscopy, high-resolution powder, and synchrotron single-crystal x-ray diffraction applied to PbSc{sub 0.5}Ta{sub 0.5}O{sub 3} (PST) and Pb{sub 0.78}Ba{sub 0.22}Sc{sub 0.5}Ta{sub 0.5}O{sub 3} (PBST). The two compounds were chosen as model systems because PST is a relaxor that exhibits ferroelectric long-range order on cooling, whereas PBST shows canonical relaxor behavior. The temperature evolution of phonon anomalies and the pseudocubic unit-cell parameter for both PST and PBST reveals the existence of a characteristic temperature T* between the Burns temperature T{sub B} and the temperature of the dielectric-permittivity maximum T{sub m}. T* is associated with the coupling of initially nucleated small polar clusters and their aggregation into larger polar clusters. The temperature range between T{sub B} and T* is characterized by a coupling between adjacent off-centered BO{sub 6} octahedra to form initial polar clusters, while the range between T* and T{sub m} is characterized by a coupling between off-centered B cations from adjacent polar clusters. Off-centered Pb atoms exist even above the Burns temperature and their length of coherence governs the coupling between polar regions comprising B-cation off-center shifts and, consequently, directs the formation of the ferroelectric state to a normal, long-range ordered or nonergodic relaxor state.

• OSTI ID: 21143536
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 77, Issue 17; Other Information: DOI: 10.1103/PhysRevB.77.174106; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AGGLOMERATION
ATOMS
BARIUM COMPOUNDS
CATIONS
COOLING
COUPLING
FERROELECTRIC MATERIALS
LEAD COMPOUNDS
MONOCRYSTALS
OXYGEN COMPOUNDS
PERMITTIVITY
PEROVSKITE
PHASE TRANSFORMATIONS
POWDERS
RAMAN SPECTRA
RAMAN SPECTROSCOPY
SCANDIUM COMPOUNDS
SOLIDS
SYNCHROTRON RADIATION
TANTALUM COMPOUNDS
X-RAY DIFFRACTION