抄録
Hard-type piezoelectric materials have been utilized in various high power applications, in which usually requires to be driven under high vibration level. However, under high stress piezoelectrics show significant nonlinear behavior, which should be taken as one of the criteria. In this study, nonlinearity in lead-free CuO-(K,Na)NbO3 transducers was investigated. The CuO-(K,Na)NbO3 transducers were cut from ceramics, which were fabricated via hydrothermal method. In the burst mode measurement, the transducers after excited by a burst excitation began free vibration. The equivalent mechanical loss and the reciprocal of equivalent stiffness were determined by velocity decay rate and resonance frequency, which were given by the velocity-time curve. The admittance curves of the transducer under high voltage were also measured via a frequency response analyzer. In the admittance curve, around the resonant frequency the values are not consecutive (jumping phenomenon); also a hysteresis appears between upward and downward sweeps, indicating the existence of nonlinearity. A model containing the nonlinear terms was proposed and adopted to fit the admittance curves. From the curve fitting the nonlinear coefficients and force factor could be determined and compared with those of Pb(Zr,Ti)O3 transducers.
