Abstract
The Raman spectra of ceramic samples of the Pb(Ti1 _x , Zr x )O3 system in its room temperature tetragonal phase have been recorded. In the frequency region of the soft phonons, the spectra show the band of the q ∼ 0 soft E(TO) mode and an additional band, absent for x = 0, centered in the 50–60 cm−1. The line-shape of the soft E(TO) phonon changes from underdamped to overdamped for x > 0.40. The x-dependence of the frequency of this mode indicates that it becomes unstable in the vicinity of the morphotropic, tetragonal-rhombohedral, phase-boundary. A brief thermodynamical discussion of the behavior of the soft E(TO) mode is given.