Investigation on co‐fired multilayer KNN‐based lead‐free piezoceramics

Potassium sodium niobate (KNN)-based lead-free piezoelectric ceramics were used to fabricate multilayer ceramics containing an Ag/Pd inner electrode via a tape casting and co-firing process. The interfacial microstructure between the electrode and ceramic was characterised using a transmission electron microscope. The apparent electric-field-induced piezoelectric response was enhanced to 452 pm V−1 by the multilayer structure. A laser Doppler vibrometer was used to test the high frequency piezoelectric properties, and a remarkable apparent dynamic response of 1839 pm V−1 with a normalised thickness strain (Smax/Emax) of 369 pm V−1 was obtained at the resonance frequency 131.8 kHz. These results indicate that KNN-based multilayer ceramics are promising substitutes for lead-based ceramics as actuators and transducers.