THE TEMPERATURE DEPENDENT PHONON SPECTRUM OF $PbTiO_{3}$.
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Date
1968
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Ohio State University
Abstract
The frequencies of the symmetry allowed $k \approx 0$ transverse and longitudinal modes were obtained from a Kramers-Kronig analysis of far infrared reflectance data taken between $80-800^{\circ} K$. Above the Curie temperature $(760^{\circ} K), PbTiO_{3}$ exhibits a broad second order Raman spectrum. For $T<T_{e}$ a strong first-order spectrum is superimposed which sharpens considerably with decreasing temperature. The $\Delta \nu/\Delta T$ of several modes is quite marked; bands observed at $760^{\circ} K$ at about 60, 120, 182, 280 and $495 cm^{-1}$ increase in frequency by about 4, 6, 8, 2 and $3.5 cm^{-1}$ respectively for each $100^{\circ}$ drop in temperature. The lowest frequency mode $(60 cm^{-1})$ is relatively the ``softest'' but the 120 and $182 cm^{-1}$ modes contribute significantly to the temperature dependence of $\epsilon_0$ and may also approach instability.
Description
This work was supported in part by the Joint Services Electronics Program (Contract DA28-043-AMC 02536 (E) ), and by a NASA Grant NGR 22-009-(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, Massachusctts Institute of Technology
Author Institution: Spectroscopy Laboratory and Research Laboratory of Electronics, Massachusctts Institute of Technology