A Raman Study of Morphotropic Phase Boundary in PbZr1-xTixO3 at low temperatures

Raman spectra of PbZr1-xTixO3 ceramics with titanium concentration varying between 0.40 and 0.60 were measured at 7 K. By observing the concentration-frequency dependence of vibrational modes, we identified the boundaries among rhombohedral, monoclinic, and tetragonal ferroelectric phases. The analysis of the spectra was made in the view of theory group analysis making possible the assignment of some modes for the monoclinic phase.Comment: 5 pages, 4 figure

Spectroscopy of Cr3+^{\bf{3+}} in ferroelectric ceramics lead-lanthanum zirconate-titanate-x/95/5 with Lanthanum content xx = 0.5 to 4 wt %

The study shows the importance of internal optical transitions $^{2}{\rm E} \to^{4}$A$_{2}$ of the excited Cr$^{3+}$ ions used as a probe of the ceramics in the microscopic scale. The results are interpreted in terms of Cr$^{3+}$ luminescent centres and simultaneous vibrational excitations of the lattice. In presence of thermally activated disorder, the PLZT-x/95/5 ferroelectric ceramics lead to interesting spectral variations with temperature by appearance of certain vibronic sidebands observed around the pure electronic transitions. The phononic origin of the process is analysed in terms of lattice perturbation in the environment of the Cr$^{3+}$ sites