New approach on interpretation and processing of Raman spectra of complex perovskites is suggested. Raman spectra of $PbMg_{ 1/3}Nb_{ 2/3}O_{ 3}$ and $% PbSc_{ 1/2}Ta_{ 1/2}O_{ 3}$ are successfully described on the basis of the phonon-confinement model and validity of the method is demonstrated on good agreement of experimentally obtained and computer simulated spectra of another complex perovskite, $BaMg_{ 1/3}Ta_{ 2/3}O_{ 3}$. The study showed that the size of nanoscale regions is a kind of an inborn characteristic of the sample and is not temperature dependent. For $PbSc_{ 1/2}Ta_{ 1/2}O_{ 3}$, two special temperature points, approximately 400 K and 600 K are found from the analysis of the temperature behaviour of obtained mode parameters.
Categories: cond-mat.mtrl-sci cond-mat.dis-nn