INFRARED AND RAMAN SPECTRA OF SOME MIXED TANTALATE PEROVSKITES.

This research was supported in part by the NSF Grant \#GP-4923 (in Spectroscopy Lab.), by ARPA, SD-90 (in Materials Center) and by Joint Service Electronics program, contract DA 28-043-AMC 02536 (E) (in Research Lab. of Electronics). $^{1}$ R. C. Miller and W. G. Spitzer, Phys. Rev. 129. 94 (1963). $^{2}$ C. H. Perry and T. F. McNelly, Phys. Rev. 154, 456 (1967).Author Institution: Spectroscopy Laboratory, Materials Center for Science and Engineering, and Research Laboratory of Electronics, Massachusetts Institute of Technology; Spectroscopy Laboratory, Materials Center for Science and Engineering, and Research Laboratory of Electronics, N.A.S.A., Electronics Research CenterThe Raman spectra of $KTaO_{2}$ and several mixed crystals $KTaO_{3}/NaTaO_{3}$ have been measured as a function of temperature using laser Raman techniques. The frequencies observed have been interpreted in terms of two phonon combinations. The slight distortion from cubic symmetry with high sodium content is not sufficient to create a first order Raman spectrum. The far infrared reflectance spectrum of the mixed crystals is similar to the pure $KTaO_{3}{^{1, 2}}$ except for a splitting of the middle frequency