Evolution of relaxor behavior and high-field strain responses in Bi(Mg1/2Ti1/2)O3-PbTiO3-Pb(Ni1/3Nb2/3)O3 ferroelectric ceramics

A composition-induced phase transition from a diffuse-type ferroelectric to a relaxor ferroelectric and then to a weak relaxor ferroelectric was observed in a new (0.68-x) Bi(Mg1/2Ti1/2)O-3-0.32PbTiO(3)-xPb(Ni1/3Nb2/3)O-3 (BMT-PT-xPNN) ternary system. Meanwhile, a gradual evolution process of nonergodic-ergodic-nonergodic realxor states was identified at room temperature from the BMT-rich side to the PNN-rich side. Two strain maxima of similar to 0.42% and similar to 0.29% under 7 kV/mmwere obtained in the x = 0.2 and x = 0.65 samples, respectively. It is worthy to note that the high-field strain of the x = 0.2 composition was thermally stable but seriously hysteretic. By comparison, the x = 0.65 composition exhibited a weakly hysteretic strain and a relatively small threshold electric field. This phenomenon was attributed to larger sizes and slower dynamics of polar nanoregions (PNRs) in BMT-rich compositions than those in PNN-rich compositions. Moreover, it was believed that the strain hysteresis of BMT-PT-xPNN relaxor ferroelectrics would be dominated by the growth process of PNRs into ferroelectric microdomains during loading and their subsequent dissociation process during unloading. (C) 2017 Elsevier B.V. All rights reserved.