Estudo por espalhamento Raman de efeitos anarmônicos e transição de fase do PbTiO3 : Sm3+ induzidos por pressão hidrostática e variação de temperatura
![Thumbnail](/bitstream/handle/ufscar/4898/TeseMACM.pdf.jpg?sequence=2&isAllowed=y)
Visualizar/ Abrir
Data
2007-10-05Autor
Machado, Marco Antonio Cunha
Metadata
Mostrar registro completoResumo
In this work it was investigated, by using Raman spectroscopy, the effect of
the substitucional disorder on the vibrational properties of the ferroelectric
ceramics PbTiO3 doped with Samarium, at different temperatures and hydrostatic
pressures. This material is interesting from the technological point of view because
it is a combination between a material with intense ferroelectric properties and a
rare earth ion, with very well known optical properties. From the academic point of
view, the main purpose was to study qualitatively and quantitatively the combined
chemical and structural effects on the phonon spectrum, which was achieved
through measurements of the frequency shifts and broadenings of the vibrational
modes, that is, the anharmonic effects. It was also investigated the changes in the
Curie temperature, the critical transition pressure values and frequency pressure
and temperature coefficients generated by substitucional disorder. A special
attention was done to the behavior of the lower frequency mode, the so called soft
mode, which plays an important role, whose frequency tends to zero with the
approach of the ferroelectric-paraelectric transition. The Raman scattering, due to
its sensitivity to short range order, to the character nondestructive, noninvasive is
a technique well adapted to the purpose of the present study. The importance of
the material and the choice of the technique are justified by the great number and
quality of publications related to both in the international literature.