THE PHONON SPECTRA AND PHASE TRANSITIONS IN THE $K(Ta:Nb)O_{3}$ MIXED CRYSTAL SYSTEM
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Date
1968
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Ohio State University
Abstract
Solid solutions of $K(Ta_{x}:Nb_{1-x})O_{3}$ have been studied by means of far infrared and Raman spectroscopy for $x = 0.0, 0.25, 0.65, 0.89$ and 1.0. Members of this series exist in cubic, tetragonal, orthorhombic and rhombohedral phases at successively lower temperatures in the range $10-800^{\circ} K$ except $KTaO_{3}$ which remains cubic. In the paraelectric (cubic) phase these materials exhibit a strong infrared reflectance spectrum and a second order Raman spectrum similar to $KTaO_{3}$. The infrared spectra are relatively unaffected through the various ferroelectric phase transitions but the Raman spectra exhibit strong first order bands which alter markedly at each structural change. Considerable hysteresis is observed in the spectra at most transitions. The infrared measurements provided a starting point for the interpretation of the Raman spectra and assignments of the phonon modes in each phase as a function of composition will be reported.
Description
This work was supported in part by the Joint Services Electronics Program (Contract DA28-043-AMC 02536(E)) and by a N.A.S.A. Grant NGR22-009-(237). Spectroscopy laboratory is supported in part by the National Science Foundation, Grant \# GP4923. Present address of C.H. Perry: Dept. of Physics, Northeastern University, Boston, Mass. 02115.
Author Institution: Spectroscopy Laboratory and Research Laboratory of Electronics, Massachusetts Institute of Technology
Author Institution: Spectroscopy Laboratory and Research Laboratory of Electronics, Massachusetts Institute of Technology