Abstract
Room-temperature Raman spectra of high-quality single-domain BaTi crystals are reported. The frequencies of the Raman-active long-wavelength optical phonons are determined and shown to be in reasonable agreement with the Lyddane-Sachs-Teller (LST) relation as well as infrared reflectivity data. The effects of mode damping on the Raman line shape are discussed using a classical lattice-polarization-fluctuation model for the Raman scattering process. Based on this model, it is shown that the soft mode is overdamped, and at 25°C has an undamped mode frequency of 36±3 and a damping constant of 1.1±0.1. The temperature dependence of is given and found to be consistent with the LST relation. The soft mode is not observed, but is estimated from the LST relation and infrared reflectivity data to be heavily damped () and to have an undamped mode frequency of 180±10 .
- Received 5 April 1968
DOI:https://doi.org/10.1103/PhysRev.174.522
©1968 American Physical Society