Neutron scattering measurements have been made of the soft mode in the uniaxial ferroelectric lead germanate for which the transition temperature is 450 K. The results are consistent with the simple soft-mode picture of the soft mode. A comparison with the results of Raman scattering measurements suggests that the latter measurements do not provide information about the one-phonon spectral function for temperatures greater than ($T_c-10\mathrm{}$) K.

• Received 11 September 1981

DOI:https://doi.org/10.1103/PhysRevB.25.6765