抄録
The frequency and linewidth of the four Raman active modes in anatase have been investigated over the temperature range 20 to 1100 K. The temperature (T) dependence of the frequency of the 639 cm−1 mode showed typical behavior in normal ionic crystals, whereas the other modes at 399, 197 and 144 cm−1 did anomalous behavior. These T dependent results were combined with pressure dependent results, thermal expansion and compressibility data to evaluate the pure-volume and pure-temperature contributions to the T dependence of each frequency. The results indicate that the anomalous T dependence of the 399 cm−1 mode reflects the near cancellation of the cubic and quartic contributions to the frequency shift, and that of the modes at 197 and 144 cm−1 arises from strong quartic contributions. The T dependence of the linewidth is well explained qualitatively in terms of simple anharmonic effects involving three phonon processes.
