High electrostrictive strain induced by defect dipoles in acceptor-doped (K_0.5Na_0.5)NbO₃ ceramics

Acceptor doping is an efficient method to improve ferroelectric material performance through the formation of defect dipoles. Here, a high electrostrictive strain of 0.160.19%, and large d∗33 of >300 pm V^-1 are obtained in CuO-doped (K_0.5Na_0.5)NbO₃ ceramics. We analyzed the orientation relationship and the interaction between defect dipole polarization (Pd) along 〈0 0 1〉 orientation and spontaneous polarization (P_s) parallel to 〈1 1 0〈 in orthorhombic (K_0.5Na_0.5)NbO₃. Thus, a coupling effect mechanism was suggested to explain how the Pd and Ps can work together to contribute to the electrostrictive strains in this lead-free piezoelectric ceramic.