Lead-free potassium sodium niobate piezoceramics for high-power ultrasonic cutting application: Modelling and prototyping

The motivation of this study was design, fabrication and characterization of bolt-clamped Langevin type transducers (BLT) from lead-free K0.5Na0.5NbO3 (KNN) based piezoceramics for high-power ultrasonic cutting applications. Hard and lead-free KNN piezoceramics was obtained by adding K4CuNb8O23 (KCN) together with ZnO and SnO2. Densification and high-power characteristics of KNN-KCN piezoceramics were enhanced in the presence of ZnO and SnO2. BLTs made from hard PZT4 (commercial Pb(Zr,Ti)O3) or Zn,Sn co-doped KNN-KCN piezoceramic rings (KNN-KCN-ZnSn) were modelled through ATILA finite element analysis software package. Simulated and experimentally measured impedance spectra, resonance modes and harmonic analysis results of BLTs were compared with each other. Longitudinal vibration displacement at the tip of the horns of BLTs at approximately 30 kHz was measured via photonic sensor device to compare their performances. At the end, based on the simulation and experimental results, a prototype ultrasonic cutting device was fabricated from lead-free KNN-KCN-ZnSn piezoceramic rings. Its cutting action on both plastic and ceramic materials was demonstrated for the first time. In summary, it was found that a hard KNN-KCN based lead-free piezoceramics were good potential replacements for their lead-based counterparts for commercial high-power BLT applications.