Induced strain piezoelectric coupling coefficient

Fig. 5.15. Variation of the induced strain piezoelectric coupling coefficient dss with the fiber volume fraction n experimental results from Chan and Unsworth [49] and finite element results from Poizat and Sester [143].

Since pyroelectric ceramics are also piezoelectric, a temperature change also induces a change in the polarization due to the secondary pyroelectric effect, which is described by the product of the thermal expansion strain times the piezoelectric coupling coefficient. While this secondary effect can be large in polymers due to their large thermal expansion coefficients, in ceramics, it is typically small compared with the (first-order) pyroelectric effect. 

The piezoelectric generator coefficient d indicates the mechanical strains that are induced by electric potentials and the piezoelectric motorcoefficient e is a measure of the dipole moments that are created by strains. These two parameters are similar in nature and proportional to one another. The electromechanical coupling coefficient k is proportional to both d and e, its square giving the efficiency of conversion between mechanical and electrical energy that can be achieved with the ferroelectric... 

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