PIEZOELECTRICITY AND PYROELECTRICITY IN FERROELECTRIC CERAMIC-POLYMER COMPOSITES

Ferroelectric composites are now an established alternative to conventional ferroelectric ceramic materials.and to the more recently discovered ferroelectric polymers. These materials due to their unique blending of polymeric properties of mechanical flexibility, formability and low cost with high electro-active properties have been been suggested to be a viable substitute both in piezoelectric and pyroelectric transducer applications. This chapter is devoted to the piezoelectric and pyroelectric properties exhibited by composites with special reference to those of 0-3 connectivity type. A review of models predicting the electroactive properties of 0-3 composites is presented together with a proposal for a new mixed connectivity cubes model to be applicable in the case of high ceramic loading and/or when the ceramic grain size incorporated in the polymer matrix is comparable to the thickness of the sample. A review of the experimental results of the piezo- and pyroelectric properties of various ferroelectric composite materials, reported by several workers, is also presented in this chapter. Special reference is made to composites made from calcium modified lead titanate and poly(vinyledene fluoride-trifluorethylene) emphasizing their advantages in the poling process which is a critical phase in the process of obtaining a successful electro-active composite.