A high electric field at different frequencies (near resonance) was applied on a piezoelectric vibrator. Current, phase between current and driven voltage, and sample temperature were measured during the operation. The results show that if an initial current in a specimen is large enough to increase sample temperature, the impedance spectra of the specimen will shift to low frequency direction during the operation. This results in the change in current, according to the shifted impedance spectra. The operation of a piezoelectric vibrator at slightly less resonance frequency will damage the vibrator more seriously than that at resonance frequency or at slightly higher resonance frequency due to the shift of impedance spectra. When a piezoelectric vibrator is operated at the frequency far away from resonance frequency, the current is not enough to increase sample temperature. In this case, the operation is safe. (C) 2003 Elsevier B.V All rights reserved.