Nonlinear Dielectric Response of Relaxor Ferroelectric (1-x)Pb(Mg1/3Nb2/3)O3 - xPbTiO3 Epitaxial Thin Films

Thin ferroelectric layers are capable of generating large dielectric and electromechanical responses at relatively low voltages, thus can be utilized in various applications including energy storage, energy harvesting, sensors, and actuators. Among ferroelectrics, relaxor ferroelectrics (1 - x)Pb(Mg1/3Nb2/3)O-3 - xPbTiO(3) are particularly interesting due to their superior dielectric and piezoelectric properties. However, dielectric and piezoelectric responses of the ferroelectric thin films are significantly suppressed relative to their bulk counterparts. The physical mechanism of the properties degradation still remains elusive, which greatly hinders their technological applications. Herein, this work systematically investigates the dielectric nonlinearity and the relationship between composition and intrinsic/extrinsic contributions of high-quality (1 - x)Pb(Mg1/3Nb2/3)O-3 - xPbTiO(3) epitaxial thin films (x = 0, 0.1, 0.32) fabricated by pulsed laser deposition. Through the Rayleigh analysis, it is found that the suppression of domain wall motion by substrate clamping is the main cause of thin film performance degradation and is further confirmed by continuous application of background dc bias to extract the dielectric response's intrinsic and extrinsic contributions. This work will pave the way for practical applications of (1 - x)Pb(Mg1/3Nb2/3)O-3 - xPbTiO(3) thin films in energy storage and electromechanical devices.