Piezos and Short Introduction of the Stack Concept

 

 Plate made of piezo material expand in the presence of an electric field E or if an electrical voltage is applied. The plate is covered on top and bottom faces with conductive material to form electrodes.Piezo actuation effect

To generate displacement with low voltages, piezo plates are stacked and  connected electrically parallel.

 

 . Piezo actuator stack design with external insulation. Homogeneous electrical field.

 

A preferred stack design of a ceramics multilayer device. The electric's layers cover the full surface of the piezo plates. There is also two external electrodes necessary to contact the multitude of "internal" electrical electrodes. Insulation is necessary between  All antipole electrodes are alternately insulated on the side faces. The unequal reciprocal internal electrodes and the two + and - external electrode strips, which provide parallel connection of all plots of the stack.  The preferrer method to do this is to realize small external insulation of the external layers and reciprocal internal electrode layers. This method has a fundamental advantage. The field in all the piezo material of a stack is ideally uniform and so there are no bent electrical field lines which would cause non-uniform mechanical stress. The lifetime of those devices is significantly increased.


The stack technology offer a benchmark solution for perfect piezo engineering: Full cover electrodes for best field homogeneity and on face insulation of the internal electrodes for excellent performance and life. 

Piezo stack actuator with full-cover electrodes
Piezo stack actuator with on-face insulation (green) of the internal electrodes.The electrodes fully cover the layers and generate homogenous filed.

Thus, the best design of a piezo plate with regard to deformation and associated mechanical stress distribution is a perfect electrostatic capacitor, where two parallel electrode plates fully cover the piezo material and generate a homogenous electric field.