Abstract: Piezoelectric ceramic thin sheets, as the core components of bimorph piezoelectric cantilever actuators, are widely used in bending devices. Currently, the correlation between the microstructure and electromechanical properties of 50~100 μm thick monolithic PZT-based ceramics remains unclear, restricting the precise control and performance optimization of thin-film PZT piezoelectric cantilever actuators. In this work, the anomalous large bending behavior of a 68 μm-thick PZT-based piezoelectric rectangular sheet (dimensions: 39 mm × 13 mm) under different electric fields after polarization was investigated. Under a cantilever configuration, a large tip displacement amplitude of 5.5 mm at the free end (effective cantilever length of 30.8 mm) was observed at the first-order resonant frequency of 38.44 Hz and an alternating electric field of 12 kV/cm. In contrast, classical piezoelectric theory predicts only in-plane uniform expansion/contraction for uniformly polarized monolithic piezoelectric thin films, with no bending effect. To address this discrepancy, in-situ X-ray diffraction (XRD), Raman spectroscopy, and piezoresponse force microscopy (PFM) were employed. The results reveal that the intrinsic lattice strain mismatch induced by surface structural asymmetry during sintering and poling provides the initial driving force for bending; the applied electric field further amplifies this strain mismatch via a reversible rhombohedral-tetragonal phase transition after poling, significantly enhancing the bending effect. This study provides theoretical and experimental support for the design and optimization of PZT-based piezoelectric cantilever actuators.

Key words: PZT-based piezoelectric ceramics, electro-induced bending, lattice strain mismatch, inverse piezoelectric effect, cantilever beam actuator