Pyroelectric activity of ferroelectric PT/PVDF-TRFE

This paper studies the pyroelectric coefficient of 0-3 composites consistin g of 27%vol lead titanate (PT) powder embedded in a vinylidene fluoride-tri fluoroethylene copolymer (PVDF-TRFE) matrix. The constituent phases of the composites have been polarized in four possible ways: only the copolymer po larized; only the ceramic polarized; the copolymer and ceramic phases polar ized in the same direction; the two phases polarized in opposite directions . The pyroelectric coefficient was measured by a dynamic method at 5 mHz wi thin the temperature range 20 to 90 degrees C (which covers the ferroelectr ic to paraelectric phase transition temperature of the copolymer matrix). T he composite with the copolymer and ceramic phases polarized in the same di rection exhibits strong pyroelectric but relatively weak piezoelectric acti vity, and vice versa when the constituent phases are oppositely polarized. A theoretical model is used to analyze the pyroelectric coefficient of the composites in terms of the pyroelectric and dielectric properties of the co polymer matrix as determined from experiment, and those of the ceramic part icles which are assumed to be temperature independent. The pyroelectric coe fficient and dielectric permittivity of the ceramic particles are obtained as fitting parameters. The theoretical prediction is found to agree well wi th the experimental data.