Composites of calcium modified lead titanate powder dispersed in a polyvinylidene fluoride/trifluoroethylene copolymer matrix have been prepared 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 permittivities of the unpoled composites are consistent with the predictions of the Bruggeman model. The changes in the pyroelectric and piezoelectric coefficients of the poled composites with increasing ceramic volume fraction can be described by modified linear mixture rules. When the ceramic and copolymer phases are poled in the same direction, the piezoelectric activities of the two phases partially cancel each other while the pyroelectric activities reinforce. Hence, at a certain ceramic volume fraction, the composite is pyroelectric but not piezoelectric.
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Chan et al. (1998) studied this question.
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