A piezoelectric element is a solid actuator that produces displacement when voltage is applied. Forming electrodes on both sides of a piezoelectric ceramic plate and applying a voltage produces a distortion of about 0.1%.
Figure 1 shows the structure of a stacked piezoelectric element. A large number of piezoelectric ceramic sheets are stacked with internal electrodes formed on opposite sides, and insulators are placed every other layer on the sides to form external electrodes.
The side surfaces of the piezoelectric element are covered with resin for protection. There is also a metal case enclosed type that blocks outside air.

The features of multilayer piezoelectric elements include: (1) large generating force, (2) high resolution, (3) high-speed response, and (4) high electromechanical conversion efficiency.

Figure 2 shows the amount of displacement when a voltage is applied to a stacked piezoelectric element. The piezoelectric element expands and contracts according to the voltage, but the displacement curves do not follow the same path when the voltage is increased (step-up) and when the voltage is decreased (step-down). This is called hysteresis (history), and it occurs at about 15 to 20% of the maximum displacement.
The displacement curve when the voltage application to the piezoelectric element is repeated several times shows a shift in the amount of displacement near a voltage of 0 V between the first and second repetitions, which is called a zero shift.

Figure 3 shows the time variation of the amount of displacement when a constant voltage is applied to the piezoelectric element and held, and it can be seen that the amount of displacement changes gradually with time.
This phenomenon is called creep and is attributed to the polarization of piezoelectric ceramics.
The amount of creep increases with the width of the input voltage from the previous voltage value, and its direction is the same as the voltage rise or fall.

Because of these properties such as hysteresis and creep, the amount of displacement of a piezoelectric element cannot be uniquely determined by the applied voltage value alone.
When piezoelectric elements are used as a drive source for precision positioning devices, it is necessary to constantly control the applied voltage while measuring the actual amount of displacement (movement) using a displacement sensor in combination.

The metal case enclosed type has a structure that shuts off the piezoelectric element from the outside air, making it less susceptible to the effects of atmospheric conditions.
Compared to piezoelectric elements with a resin exterior, they have superior durability against ambient temperature and humidity, and are less likely to deteriorate (life time) even when constant voltage is applied for a long period of time.

• Instruments and microscopes that handle liquids, such as biotechnology
• Environment with oil or mist on processing machine
• Usage in which the device remains stationary dwell (in standby) at a fixed position for a long period of time * The time in which the device is in operation is shorter.
• Usage in which the device remains stationary dwell (in standby) at a fixed position for a long period of time
  * The time in which the device is in operation is shorter.
• Use in locations where replacement (removal) is difficult in the event of failure
• Applications requiring high reliability
• High vacuum, ultra-high vacuum