Ferroelectric and structural instability in double perovskites Me{sup 1+}Bi{sup 3+}Me{sup 3+}Nb{sup 5+}O{sub 6} (Me{sup 1+} = Na, K, Rb; Me{sup 3+} = Sc, Ga, In, Lu)
- Russian Academy of Sciences, Kirenskii Institute of Physics, Siberian Branch (Russian Federation)
Within the Gordon-Kim generalized model with regard to the polarizabilities of ions, the lattice constants, the high-frequency permittivity, the Born dynamic charges, and the vibration constants of the crystal lattice are calculated for cation-ordered double perovskites Me{sup 1+}Bi{sup 3+}Me{sup 3+}Nb{sup 5+}O{sub 6}. The vibration spectra of all the compounds exhibit two types of instabilities: instability associated with the rotation of the oxygen octahedron and ferroelectric instability. Various combinations of distortions with respect to the rotation mode yield five energetically most favorable distorted phases. The symmetry and the energy characteristics of these phases are discussed. In four of the five phases, the distortions associated with the oxygen octahedron rotation lead to polar phases, thus allowing one to speak of improper ferroelectricity in these compounds. One phase turns out to be nonpolar; however, it contains unstable polar modes such that a displacement along the eigenvectors of these modes gives rise to polarization in the crystal.
- OSTI ID:
- 22069452
- Journal Information:
- Journal of Experimental and Theoretical Physics, Vol. 114, Issue 6; Other Information: Copyright (c) 2012 Pleiades Publishing, Ltd.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7761
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
36 MATERIALS SCIENCE
CRYSTAL LATTICES
CRYSTALS
EIGENVECTORS
FERROELECTRIC MATERIALS
GALLIUM COMPOUNDS
INDIUM COMPOUNDS
LATTICE PARAMETERS
LUTETIUM COMPOUNDS
NIOBATES
PERMITTIVITY
PEROVSKITES
POLARIZABILITY
POLARIZATION
POTASSIUM COMPOUNDS
ROTATION
RUBIDIUM COMPOUNDS
SCANDIUM COMPOUNDS
SODIUM COMPOUNDS