POLARIZED RAMAN AND ELECTRICAL STUDY OF SINGLE-CRYSTALLINE TITANIUM-MODIFIED LEAD MAGNESIO-NIOBATE

Raman scattering experiments were performed on the relaxer ferroelectr ic lead magnesio-niobate (PMN), the ferroelectric 0.8 PMN-0.2 PbTiO3 ( PT) and the intermediate composition 0.9 PMN-0.1 PT. In order to under stand in more detail the behaviour of this series, Raman scattering sp ectra were also collected under de electric held. A ferroelectric phas e could be induced in the latter composition for electric fields highe r than a threshold value. The behaviour of this field-induced phase wa s compared with the (zero-field) ferroelectric phase in 0.8 PMN-0.2 PT . Barkhausen jumps were observed in the pyroelectric current measureme nts, and a strong dielectric anomaly was detected in zero field heatin g after field cooling experiments on 0.9 PMN-0.1 PT. These results are consistent with a description of the behaviour in this series based o n a cancellation of 1:1 (Mg:Nb) domain random freIds by titanium ions, favouring the onset of long range ferroelectric order.