PHYSICAL REVIEW B, cilt.71, sa.9, 2005 (SCI-Expanded)
Dielectric, anelastic, and La-139 NMR relaxation measurements have been made on the relaxor ferroelectric Pb1-3x/2La.Zr0.2Ti0.8O3 (PLZT) with x=0.22. The dielectric susceptibility exhibits the frequency dispersive maximum due to the freezing of the polar degrees of freedom around T 250 K. The anelastic and especially NMR relaxation, besides this maximum, indicate an intense and broad component at lower temperatures, attributed to rotational modes of the O octahedra, weakly coupled to the polar modes. It is discussed why such short range rotational instabilities, known to occur in the Zr-rich rhombohedral region of the PLZT phase diagram, might appear also in the Ti-rich region.