Combining XRD and Raman spectroscopy techniques to probe the solid solution and composite forms of Pb1-xCoxTiO3 systems

Raman scattering and XRD data allied to Rietveld refinement were used to investigate the structural and vibrational properties of Pb1-xCoxTiO3 samples with x ranging from 0.0 to 1.0. The results showed reductions in the tetragonallity factor and in the wavenumber of E(1TO) soft mode in the interval between x = 0.0 (c/a = 1.063 and E(1TO) = 89 cm(-1)) and x = 0.2 (c/a = 1.042 and E(1TO) = 81 cm(-1)). These parameters present a partial recovery for x > 0.4. Quantitative phase analyses combined with SEM indicate the formation of a solid solution for x less than 0.2 and composite formation of PbTiO3 and CoTiO3 for x higher than 0.2. From the temperature-induced softening of the E(1TO) mode, it was investigated the effect of the atomic substitution on the PbTiO3 Curie temperature, showing a minimum at 720 K (x similar to 0.4) compared to 763 K (x = 0).