LATTICE DYNAMICS AND PHASE TRANSITIONS OF STRONTIUM TITANATE

Journal Article · Mon May 18 04:00:00 EDT 1964 · Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D

DOI:https://doi.org/10.1103/PhysRev.134.A981· OSTI ID:4031106

Cowley, R A

The crystal dynamics of strontium titanate was studied both experimentatly and theoretically. The frequency versus wave-vector dispersion curves for some of the normal modes propagating along the STA0,0,1! direction were measured by neutron spectrometry at 90 and 296 deg K. The experiments were performed at the Chalk River Laboratories of Atomic Energy of Canada Ltd., using a triple-axis crystal spectrometer. The temperature dependence of the transverse optic mode of the lowest frequency was found to be in agreement with the temperature dependence of the dielectric constant, as predicted by Cochran. The experimental results were used to obtain the parameters of several models, more than one of which gives reasonable agreement with the experimental results. It is suggested that the anomalous behavior of the elastic properties and the phase transition at 100 deg K are associated with an accidental degeneracy of two branches of the dispersion curves: the longitudinal acoustic branch and the transverse optic branch of lowest frequency. The origin of the temperature dependence of this transverse optic mode and the relevance of lattice dynamics to the phase transitions in other perovskites are discussed. (auth)

• Research Organization: Cambridge Univ., Eng.
• NSA Number: NSA-18-019992
• OSTI ID: 4031106
• Journal Information: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D, Journal Name: Physical Review (U.S.) Superseded in part by Phys. Rev. A, Phys. Rev. B: Solid State, Phys. Rev. C, and Phys. Rev. D Vol. Vol: 134; ISSN PHRVA
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ALLOTROPY
CHEMISTRY
CRYSTAL COUNTERS
CRYSTALS
DIAGRAMS
DIELECTRICS
ELASTICITY
FREQUENCY
LOW TEMPERATURE
NEUTRON SPECTROMETERS
OPTICAL MODEL
PHASE DIAGRAMS
PHASE TRANSFORMATION
STRONTIUM OXIDES
TEMPERATURE
TITANIUM OXIDES
VECTORS