Limitations of Piezoelectric Actuators

In static operations, the lifetime is mainly limited by the humidity, which penetrates through the external insulation layer and leads to a leakage current increase. A larger leakage current can lead to an electrical breakdown. Due to the dielectric and mechanical losses, the piezoelectric actuator warms up under continuous excitation. Losses are mainly non-linear and depend on the excitation frequency, the voltage amplitude and the humidity. To avoid a depoling effect of the ceramic, the temperature in the actuator should be monitored to ensure that it stays well below the ceramics Curie temperature. So a typical range of temperatures is —40°C to 80 °C. 

This results in that the duty cycle of the piezoelectric actuator in dynamic operation is limited by the thermal behaviour. 

There are currently a lot of research into materials capable of producing MLAs displaying higher working temperatures (up to 140°C). Similarly, the standard MLAs work at low temperature and have already been tested in liquid nitrogen (77K, -196°C) at this low temperature, their displacement is only one third of that obtained at room temperature. 

Provided the self heating and the tensile forces are prevented, the amplified piezo actuators do not show any fatigue effect. For example, a test of an amplified piezo actuator imder full scale pulse (0... 150 V) with a driving frequency of 600 Hz, had a continuous duration of 6 months. It shows the ability of the actuator to operate for 10 ° cycles. 

The thermo-mechanics may be an issue in the case of a fine positioning application over a large range of temperature the PZT in the multilayer technique display various coefficient of thermal expansion, CTE (as a function of some construction details). Standard amplified piezo actuators displays fairly large CTE due to some thermal mismatch between the piezo component and the shell material. There are some possibilities to cancel this CTE in the application  

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