VARIATIONS OF PHYSICAL-PROPERTIES ACCORDING TO FERROELECTRIC-PARAELECTRIC PHASE-TRANSITION IN PMN-BASED RELAXOR FERROELECTRICS

In order to understand the ferroelectric-paraelectric phase transition and related physical properties, polarizations and strains induced by bipolar electric field as well as those induced by unipolar electric field were measured in 0.9 Pb(Mg-1/3 Nb-2/3)O-3 - 0.1PbTiO(3) relaxer ferroelectric ceramics in the temperature range of -50 similar to 90 d egrees C. From the temperature dependence of the electrostrictive comp onent (PuniSuni) and the piezoelectric component (P-r,S-r), it was sho wn quantitatively how the phase transition from totally electrostricti ve to partially piezoelectric properties occurs. From the temperature dependence of impedance spectrum of the samples, it was shown schemati cally that magnitude of electromechanical coupling factor becomes smal ler as the temperature increases up to the phase transition range.