Transition dynamics in ferroelectrics with ordered nanoregions
- Univ. of Puerto Rico, San Juan (Puerto Rico). Dept. of Physics
Raman scattering was used to study two model relaxor ferroelectrics, PbMg{sub 1/3}Nb{sub 2/3}O{sub 3} (PMN) with the 1:2 stoichiometric composition of Mg{sup 2+} and Nb{sup 5+} ions in the oxygen octahedrons and PbSc{sub 1/2}Ta{sub 1/2}O{sub 3} (PST) with the 1:1 stoichiometric composition of Sc{sup 3+} and Ta{sup 5+} ions. In spite of a different stoichiometric ratio the Raman spectra of both materials are consistent with the Fm3m space symmetry which implies the existence of similar 1:1 ordered clusters at least in nanoscale regions. The spectra show some anomalous features in the temperature range preceding a ferroelectric state, namely a broad central peak appears in PMN and a complex structure develops from the initially singlet line in PST. Those phenomena are considered as the dynamic features in course of evolution of the relaxors to a ferroelectric state. The preceding phase is characterized by a breakdown in the selection rules for Raman scattering, so some points in the Brillouin zone can contribute to the light scattering spectra. Comparing all available data, one can assume the determinant role of heterophase fluctuations in that process. The fluctuations in a special preceding phase are caused by a competition between two phases, namely between the ferroelectric phase and an additional nonpolar phase.
- Sponsoring Organization:
- National Aeronautics and Space Administration, Washington, DC (United States); USDOE, Washington, DC (United States); National Science Foundation, Washington, DC (United States)
- OSTI ID:
- 522284
- Report Number(s):
- CONF-961202-; ISBN 1-55899-361-4; TRN: 97:014705
- Resource Relation:
- Conference: 1996 Fall meeting of the Materials Research Society (MRS), Boston, MA (United States), 2-6 Dec 1996; Other Information: PBD: 1997; Related Information: Is Part Of Nanophase and nanocomposite materials 2; Komarneni, S. [ed.] [Pennsylvania State Univ., University Park, PA (United States)]; Parker, J.C. [ed.] [Nanophase Technologies Corp., Burr Ridge, IL (United States)]; Wollenberger, H.J. [ed.] [Hahn-Meitner Inst., Berlin (Germany)]; PB: 573 p.; Materials Research Society symposium proceedings, Volume 457
- Country of Publication:
- United States
- Language:
- English
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