Actuator
Below the Curie temperature, the materials show a spontaneous polarisation.This spontaneous polarisation is caused by the displacement of ions of the elementary cell, which results in the loss of the centre of symmetry The main areas of the positive and negative charges are no longer to be found in the centre of the elementary cell of the crystal. The elementary cell possesses an electric dipole.
The piezoelectric properties of the ceramics important for industry are only produced by this polarisation process. In this case, the ceramics are exposed to a very strong electric field.
