PYROELECTRIC AND PIEZOELECTRIC PROPERTIES OF LEAD TITANATE POLYVINYLIDENE FLUORIDE-TRIFLUOROETHYLENE 0-3-COMPOSITES/

Composites of calcium modified lead titanate powder dispersed in a pol yvinylidene fluoride/trifluoroethylene copolymer matrix have been prep ared using solvent casting followed by compression molding. Two groups of poled samples have been prepared: one with only the ceramic phase polarized and the other with both phases polarized. The observed permi ttivities of the unpoled composites are consistent with the prediction s of the Bruggeman model. The changes in the pyroelectric and piezoele ctric coefficients of the poled composites with increasing ceramic vol ume fraction can be described by modified linear mixture roles. When t he ceramic and copolymer phases are poled in the same direction, the p iezoelectric activities of the two phases partially cancel each other while the pyroelectric activities reinforce. Hence, at a certain ceram ic volume fraction, the composite is pyroelectric but not piezoelectri c.