Analysis of nonlinear phenomena in piezoelectric ceramics under high-power vibration

Generation of higher harmonic voltages in piezoelectric ceramics driven at high-power resonance frequency levels was investigated. Rectangular bar samples with a high mechanical quality factor were prepared for this study. The samples were driven at a fundamental resonance frequency of the length extensional vibration mode by a constant current method, and their current, voltage and displacement were simultaneously measured. When the samples were driven at a constant current higher than the threshold level, distinct distortion in voltage waveform was observed while current waveform and displacement were exactly sinusoidal. By analyzing the distorted voltage waves with ii spectrum analyzer, the distortion of the voltage wave was found to be due to the generation of higher harmonic voltages. The 2nd and 3rd harmonic voltages were measured as a function of current, and their magnitudes satisfied the power laws of square and cubic of the current, respectively. These experimental results can be explained by nonlinear piezoelectric equations derived from the ferroelectric theory.