Raman scattering from relaxor ferroelectrics and related compounds

It is shown that Raman scattering can provide useful information about the behaviour of the correlation function of the polarization and the degree of ferroelectric ordering (through Raman Selection Rules) in relaxer systems. These considerations are illustrated by results on La-modified lead zircon ate titanate (PLZT), Ti-modified lead magnesio-niobate (PMN-PT) and Zr-modi fied barium titanate (BTZ). In addition, a new low temperature state in PLZ T, demonstrated by Raman scattering and electrical properties experiments, is reported and discussed.