Dielectric Relaxor Evolution and Frequency‐Insensitive Giant Strains in ( Bi 0.5 Na 0.5 ) TiO 3 ‐Modified Bi ( Mg 0.5 Ti 0.5 ) O 3 – PbTiO 3 Ferroelectric Ceramics

The 0.45 Bi ( Mg 0.5 Ti 0.5 ) O 3 –(0.55 −  x ) PbTiO 3 – x ( Bi 0.5 Na 0.5 ) TiO 3 ( BMT – PT – x BNT ) ternary solid solution ceramics were prepared via a conventional solid‐state reaction method; the evolution of dielectric relaxor behavior and the electrostrain features were investigated. The XRD and dielectric measurements showed that all studied compositions own a single pseudocubic perovskite structure and undergo a diffuse‐to‐relaxor phase transition owing to the evolution of the domain from a frozen state to a dynamic state. The formation of the above dielectric relaxor behavior was further confirmed by a couple of measurements such as polarization loops, polarization current density curves, as well as bipolar strain loops. A large strain value of ~0.41% at a driving field of 7 kV/mm (normalized strain d 33 * of ~590 pm/V) was obtained at room temperature for the composition with x  = 0.32, which is located near the boundary between ergodic and nonergodic relaxor. Moreover, this electric field‐induced large strain was found to own a frequency‐insensitive characteristic.