Abstract
Raman scattering was studied in model relaxor ferroelectrics PbSc1/2Ta1/2O3PST) and PbMg1/3Nb2/3O3(PMN) (both single crystals) and in related low-permittivity materials SrAl1/2Ta1/2O3 (SAT), SrAl1/2Nb1/2O3 (SAN) and BaMg1/3Ta2/3O3 (BMT) (all ceramics). A comparative analysis of the Raman spectra suggests that these complex perovskites consist of nanoscale clusters with the 1:1 B-site order, irrespective of (1:1 or 1:2) B cations stoichiometric composition. This result is in agreement with the recent microstructure studies of both PST and PMN, by direct methods. The low-permittivity compounds reveal the basic static spectrum corresponding to 1:1 or 1:2 composition, which is modified in relaxors by dynamic effects in the course of evolution to the ferroelectric state. PST and PMN clearly show such dynamic effects as mode broadening and a central peak.
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