Preparation and characterization of novel piezoelectric and pyroelectric polymer electrets

The preparation and characterization of novel piezoelectric and pyroelectri c electrets is discussed with respect to their electret properties. Charged heterogeneous electrets, like closed-cell microporous polypropylene (PP) f oams and 'soft-hard' fluoropolymer hybrids are shown to yield large quasi-s tatic and dynamic piezoelectric responses, indistinguishable from true piez oelectricity. Piezoelectric coefficients comparable to that of ceramic coun terparts have been achieved. For the investigation of the piezoelectric and pyroelectric properties of the electret materials, the thermal-pulse techn ique has been extended towards temperature-dependent investigations and mea surements on planar, cylindrical or spherical samples. The potential of the thermal-pulse technique not only for the measurement of electric-field and polarization distributions, but also for acoustical, electromechanical and pyroelectric properties is outlined.