Piezoelectric coefficient

Piezoelectric coefficient or Piezoelectric Modulus, aka D₃₃, quantifies the volume change when a piezoelectric material is subject to an electric field, or the polarization on application of a stress: d = P σ where P is polarization, and σ is the stress.

There are actually many Piezoelectric coefficients: D_xy.

See Piezoelectricity#Mechanism.