Stress-relaxation-induced enhancement of piezoelectric response in 0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ thin films

High-performance piezoelectric thin films are critical for next-generation microelectromechanical systems and flexible electronic devices, yet the properties are often limited by lattice mismatch/thermal treating induced stress. Here, stress in the sol-gel prepared 0.7 Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (PMN-PT) thin film was partially released by using a LaNiO₃-buffered Mica substrate, yielding a substantial enhancement in piezoelectric performance. X-ray diffraction analysis showed that the 100 diffraction peak of the PMN-PT film grown on LaNiO₃/Mica shifted to a higher angle and was closer to the intrinsic 100 peak position of PMN-PT, indicating substantial relaxation of the substrate-induced in-plane compressive stress. Meanwhile, this substrate promoted highly 100-oriented growth with a texture fraction of 97.9%, lowered the coercive field to 8.9 kV/cm, and reduced the leakage current to below 10−8 A. Importantly, the effective piezoelectric coefficient d₃₃∗ increased from ∼85 p.m./V on the rigid Pt/Si substrate to ∼121 p.m./V, corresponding to an enhancement of ∼42%. The film further exhibited robust and reversible ferroelectric domain switching with excellent polarization stability after 106 switching cycles. These results demonstrate an efficient substrate-engineering route for optimizing ferroelectric thin-film performance and provide a practical foundation for developing flexible, fatigue-resistant, and high-efficiency piezoelectric devices.