Lattice dynamics, ferroelectric and antiferroeelctric instabilities, and the ferroelectric phase transition in disordered PbB'{sub 1/2}B''{sub 1/2}O{sub 3} (B' = Ga, In, Lu; B'' = Nb, Ta) solid solutions

Journal Article · Sun Jun 15 04:00:00 EDT 2008 · Journal of Experimental and Theoretical Physics

DOI:https://doi.org/10.1134/S1063776108060101· OSTI ID:21244161

Zamkova, N G; Zinenko, V I ^[1]

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1. Russian Academy of Sciences, Kirensky Institute of Physics, Siberian Branch (Russian Federation)

The lattice vibration spectra, rf permittivity, and dynamic Born charges of disordered PbB'{sub 1/2}B''{sub 1/2}O{sub 3} (B' = Ga, In, Lu; B'' = Nb, Ta) solid solutions are calculated in terms of the generalized Gordon-Kim model. All the compounds are found to have soft modes related to the center ({gamma}{sub 15}) and boundary point R (R{sub 15}) of the Brillouin zone; the frequencies of these modes are close. The ferroelectric phase transition temperatures and the spontaneous polarization in the ferroelectric phase are calculated for the solid solutions using a model Hamiltonian in the local mode approximation and the Monte Carlo method. These temperatures for the tantalum compounds are found to be higher than for the niobium compounds, and temperature t{sub s} increases with the atomic number of ion B'. A model where the antiferroelectric state is related to the condensation of modes {gamma}{sub 15} and R{sub 15} is proposed. It is found that, for all compounds except for PbSc{sub 1/2}Nb{sub 1/2}O{sub 3} and PbSc{sub 1/2}Ta{sub 1/2}O{sub 3}, the ferroelectric phase, which is only related to the condensation of mode R{sub 15}, and the antiferroelectric phase have similar energies. In PbIn{sub 1/2}Ta{sub 1/2}O{sub 3}, the antiferroelectric phase turns out to be energetically favorable.

• OSTI ID: 21244161
• Journal Information: Journal of Experimental and Theoretical Physics, Journal Name: Journal of Experimental and Theoretical Physics Journal Issue: 6 Vol. 106; ISSN JTPHES; ISSN 1063-7761
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANTIFERROELECTRIC MATERIALS
APPROXIMATIONS
BRILLOUIN ZONES
FERROELECTRIC MATERIALS
GALLIUM COMPOUNDS
HAMILTONIANS
INDIUM COMPOUNDS
INSTABILITY
LEAD COMPOUNDS
LUTETIUM COMPOUNDS
MONTE CARLO METHOD
NIOBIUM COMPOUNDS
PERMITTIVITY
PHASE TRANSFORMATIONS
POLARIZATION
SOLID SOLUTIONS
TANTALUM COMPOUNDS
TRANSITION TEMPERATURE