Transition between the relaxor and ferroelectric states for (1−x)Pb(Mg1∕3Nb2∕3)O3–xPbTiO3 with x=0.2 and 0.3 polycrystalline aggregates

The transition between the relaxor and ferroelectric states for 0.8Pb(Mg1∕3Nb2∕3)O3–0.2PbTiO3 and 0.7Pb(Mg1∕3Nb2∕3)O3–0.3PbTiO3 polycrystalline aggregates has been studied by measurements of the dielectric and elastic properties as a function of temperature. The ferroelectric to relaxor transition seems to present a regime of ferroelectric fluctuations that is sharply interrupted by the appearance of the polar nanodomains. It also presents thermal hysteresis, not only in the transition temperature, Tc, but in the characteristic time scale of the ferroelectric fluctuations that is longer on cooling than on heating. The latter effect is much more significant for 0.8Pb(Mg1∕3Nb2∕3)O3–0.2PbTiO3 (Tc=346K on heating), than for 0.7Pb(Mg1∕3Nb2∕3)O3–0.3PbTiO3 (Tc∼408K on heating). This indicates that there is a sharp slowing down of the kinetics of the phase transition below 346 K.