Direct observation of relaxation modes in KNbO/sub 3/ and BaTiO/sub 3/ using inelastic light scattering

Journal Article · Fri Jul 01 00:00:00 EDT 1988 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.38.597· OSTI ID:7031766

Sokoloff, J P; Chase, L L; Rytz, D

Cubic and tetragonal BaTiO/sub 3/ and orthorhombic KNbO/sub 3/ have been studied by Raman scattering, using an iodine filter to eliminate elastically scattered light. In addition to the usual phonon features, such as the soft E mode in tetragonal BaTiO/sub 3/ and the soft B/sub 2/ mode in orthorhombic KNbO/sub 3/, central components have been observed in both materials for the first time. These components have the linewidths, line shapes, and thermal properties of relaxation modes, and symmetry properties consistent with an eight-site order-disorder model of the successive phase transitions. Additionally, the data provide direct evidence that clusters of precursor order are present in cubic BaTiO/sub 3/ and the model provides estimates of the temperatures at which these clusters are present in both BaTiO/sub 3/ and KNbO/sub 3/. These values are in good agreement with the results of linear birefringence and refractive-index measurements.

• Research Organization: Physics Department, Indiana University, Bloomington, Indiana 47401
• OSTI ID: 7031766
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Vol. 38:1
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM COMPOUNDS
PHONONS
RAMAN SPECTRA
POTASSIUM COMPOUNDS
BIREFRINGENCE
CUBIC LATTICES
INELASTIC SCATTERING
LINE WIDTHS
NIOBATES
ORDER-DISORDER TRANSFORMATIONS
ORTHORHOMBIC LATTICES
REFRACTIVITY
RELAXATION
TETRAGONAL LATTICES
THERMODYNAMIC PROPERTIES
TITANATES
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
NIOBIUM COMPOUNDS
OPTICAL PROPERTIES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
QUASI PARTICLES
REFRACTION
REFRACTORY METAL COMPOUNDS
SCATTERING
SPECTRA
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360603* - Materials- Properties