Study of the piezoelectric properties of 1-3 composites as a function of the mechanical characteristics of the phases

The behaviour of the electromechanical parameters (d31, Kp) of biphasic composite materials has been studied as a function of the relative elastic compliances of the phases and the volumetric fraction of the piezoelectrically active phase, a ferroelectric ceramic in the systems under consideration. The mathematical expressions for the dielectric and piezoelectric parameters obtained from models of 1-3 connectivity composites were the starting point for this study.1,2The discussion has taken into consideration different values of d,31 and d33. Values for lead titanatezirconate and lead-calcium titanate, the latter having a high piezoelectric anisotropy, have been considered.The results show that the low coupling of the planar mode of the resonance in the composite disk is strongly dependent on the relative elastic compliances of the component phases, as well as on the d3l/d33 ratio of the ceramic phase. Additionally, this analysis reveals that it is possible to get a value of Kp of the composite, which is virtually zero, simply by varying the ratio between the elastic compliances of the phases, even when the composite exhibits a nonzero value of the d31 coefficient. A high ratio between elastic compliances of the matrix and the ceramic SMij/SEij will result in values of Kp of the composite very close to zero.

Keywords:

• composites
• piezoelectrics
• sensors