Piezoelectric and pyroelectric properties of PZT/P(VDF-TrFE) composites with constituent phases poled in parallel or antiparallel directions

Composites of lead zirconate titanate (PZT) powder dispersed in a vinyliden e fluoride-trifluoroethylene copolymer [P(VDF-TrFE)] matrix have been prepa red by compression molding. Three groups of polarized samples have been pre pared by poling: only the ceramic phase, the ceramic and polymer phases in parallel directions, and the two phases in antiparallel directions. The mea sured permittivities of the unpoled composites are consistent with the pred ictions of the Bruggeman model. The changes in the pyroelectric and piezoel ectric coefficients of the poled composites with increasing ceramic volume fraction can be described by modified linear mixture rules. When the cerami c and copolymer phases are poled in the same direction, their pyroelectric activities reinforce while their piezoelectric activities partially cancel. However, when the ceramic and copolymer phases are poled in opposite direc tions, their piezoelectric activities reinforce while their pyroelectric ac tivities partially cancel.