Shear-structured piezoelectric accelerometers based on KNN lead-free ceramics for vibration monitoring†

The process of promoting the transition of piezoelectric devices to lead-free requires consideration from multiple dimensions, including materials, devices and processes. In the key field of vibration monitoring, there has been a notable lack of attention paid to the shear mode of lead-free piezoelectric ceramics, leaving a gap in research on shear-mode accelerometers utilizing lead-free perovskite-structured ceramics. In this study, potassium sodium niobate (KNN)-based benign piezoelectric ceramics were synthesized and their complete set of material constants were characterized. Leveraging the higher shear piezoelectric coefficient of the ceramics, an annular shear-structured piezoelectric accelerometer based on KNN ceramics was successfully fabricated for the first time. Simulation and experiment verified that the shear-structured sensor exhibits good charge sensitivity (S_q = 9.49 pC g⁻¹), low nonlinearity (<1%) within a range of 0.5–20 g, and stability in both sensitivity and phase angle with fluctuations within ±5% across a frequency range of 20 Hz to 3000 Hz. In addition, we propose that using the effective piezoelectric coefficient (d_ij (eff)) is an important guiding significance for evaluating the practical application performance of piezoelectric materials. This research will promote the practical application of lead-free piezoelectric ceramics in the field of vibration monitoring.