Influence of nanoscale regions on Raman spectra of complex perovskites

New approach on interpretation and processing of Raman spectra of complex perovskites is suggested. Raman spectra of $PbM{g}_{1\mathrm{/}3}N{b}_{2\mathrm{/}3}{O}_3$ 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, $BaM{g}_{1\mathrm{/}3}T{a}_{2\mathrm{/}3}{O}_3$. 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 $PbS{c}_{1\mathrm{/}2}T{a}_{1\mathrm{/}2}{O}_3$, two special temperature points, approximately 400 K and 600 K are found from the analysis of the temperature behaviour of obtained mode parameters.