(1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-xPT), regarded as relaxor ferroelectrics, is one of the most important materials in applications because of their high electro-mechanical coupling coefficient near the morphotropic phase boundary (MPB) located at x = 9%. Such relaxors are known to undergo the diffuse phase transition with a broad peak in the dielectric permittivity as a function of temperature owing to heterogeneity such as polar nanoregions (PNRs). However, the physical mechanism for the appearance of relaxor properties seems to be still controversial. On the other hand, the critical endpoint (CEP) has been found in (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 being isomorphous compound of PZN-xPT [1]. In a series of our studies, we have investigated the temperature dependence of the permittivity under the dc biasing field in PZN-xPT, and have found that the broad peak in the permittivity changes to the sharp peak under the dc biasing field, suggesting the existence of CEP on the temperature-field phase diagram [2]. In the present study, to reinforce our previous conclusion that the CEP certainly exists, we have observed double hysteresis loops in PZN-9%PT showing the field induced transition just above the first-order transition temperature. It has been found that the hysteresis of the double loops disappears at CEP located at 190oC and 1.2 kV/cm.
References
[1] Z. Kutnjak et al.: Nature 441, 956 (2006).
[2] M. Iwata et al.: Phase Transitions 88, 306 (2015).