2ND-ORDER DIELECTRIC PERMITTIVITY OF PT P(VDF-TRFE) 0-3-COMPOSITES/

For a fundamental understanding of a composite material comprising two ferroelectrics and also with respect to applications, it is important to know the degree of poling in the two constituent phases. The secon d order dielectric permittivity of 0-3 composites of lead titanate (PT ) and vinylidene fluoride-trifluoroethylene (PVDF-TrFE), with various volume fractions of the ceramic phase, is reported. Composites with on ly the ceramic phase polarized, i.e. poled at temperature above the Cu rie temperature of the copolymer and below the Curie temperature of th e ceramics, and composites with both the ceramic and the copolymer pha ses polarized have been studied. The experimental results have been an alyzed with a model of ferroelectric cuboides embedded in a ferroelect ric matrix. The contributions of the ceramic and copolymer phases to t he second order permittivity have been separated, thereby giving the d egree of poling in each of the two phases.