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.