Raman Spectrum of Potassium Tantalate

Abstract

The Raman spectrum of KTaO3 has been measured as a function of temperature from 300° to 8°K. An argon-ion laser was used as the illuminating source and the scattered light was analyzed with an in-tandem grating spectrometer. The spectrum consisted entirely of second-order Raman processes originating for the most part from the Brillouin zone boundary where the combined density of states tends to be very large. No first-order Raman spectra were observed, in agreement with the known selection rules for the cubic perovskite structure. The scattering tensor deduced from the observed spectra appeared to be largely if not entirely diagonal, but the magnitude and sign of the individual diagonal elements were not investigated. Further, the predominant structural features of the spectrum are due to combinations and overtones between transverse modes. Two rather weak longitudinal overtones were found and other similar two-phonon spectra might be hidden under other more intense spectra.