Piezoelectric properties of (Na1-xKx)NbO3-based lead-free piezoelectric ceramics and their application in knocking sensor

Abstract

Piezoelectric knocking sensors with a dense microstructure were fabricated at 960 degrees C for 2hours using various CuO-added (Na0.5K0.5)NbO3 (NKN)-based piezoelectric ceramics. The practical sensitivity (S-P) of the knocking sensor, which is the ability to detect the knocking of a car engine, was influenced by the g(33) x k(p) value of the piezoelectric ceramics, indicating that the g(33) x k(p) can be considered a figure of merit of the piezoelectric ceramics used in the knocking sensor. The knocking sensor synthesized using the CuO-added 0.95(Na0.5K0.5)(Nb0.95Sb0.05)O-3-0.05CaTiO(3) (CNKNS-CT) ceramic, which showed a g(33) of 25.7Vm/N and k(p) of 0.46, exhibited a high S-P of 119mV/g at the resonance frequency. The S-P of the commercial knocking sensor, which was synthesized using the Pb(Zr,Ti)O-3 (PZT)-based ceramic, was 112mV/g at the resonance frequency. Hence, the knocking sensor fabricated using the CNKNS-CT piezoelectric ceramic can be used to replace the commercial PZT-based knocking sensor.