VIBRATION ABSORPTION OF PZT PIEZOELECTRIC CERAMICS

Recently, sound and mechanical vibration are becoming important problems in our life. In order to absorb vibrations, the input vibration energy has to be transformed into other kind of energy which can be emitted out to the surrounding easily. Piezoelectric ceramics have a function of transforming mechanical energy into electric energy by changes in the direction of the spontaneous polarization. Mechanical input vibration of 1 kHz was produced continuously by the actuator. The electric charge produced by the piezoelectric effect was measured in open state (both electrodes are not connected to anywhere), short state (both electrodes are connected each other) and ground state (one or both electrodes are connected to the ground). Then, the vibration absorption characteristics were measured. They showed very large values at the ground state. The transformation of vibration energy into electric charge by the piezoelectric effect was identified by observing the maximum charge at the resonant frequency. The produced electric charge and vibration absorption increased with the increase in electromechanical coupling factor and piezoelectric coefficient. In case of the internal insertion of electrode such as multilayer ceramics, however, elastic and dielectric losses compensated the contribution of piezoelectric coefficient and electromechanical coupling factor to the production of electric charge and gave a low charge and a low vibration absorption efficiency.