Studies of PZT/P (VDF-TrFE) 0-3 composites

Abstract

0-3 composites of lead zirconate titanate / vinylidene fluoride-trifluoroethylene, PZT/P(VDF-TrFE) were fabricated by dispersing the PZT ceramic powder in P(VDF-TrFE) copolymer. Sample discs with different ceramic volume fractions ? were produced by hot pressing. The samples were annealed at 120C for 2 hours and the microstructure was studied by scanning electron microscope and X-ray diffraction method. The dielectric permittivities within the temperature range of -30 C to 125 C during heating and cooling and in the frequency range of 100 Hz to 10 MHz were found by the impedance analyzer under computer control. The samples were then poled by applying a d.c. field at different temperatures. Two groups of samples were prepared, with a) only the ceramic phase poled, b) the ceramic and copolymer phases poled in the same direction. The piezoelectric coefficient dh was measured under hydrostatic pressure, the d33 was measured by the d33 meter and the d31 was found by calculation. The pyroelectric coefficient of the composites was measured by the dynamic method. The contribution of the secondary pyroelectric effect was estimated and found to be negligibly small. Experimental results are found to agree quite well with the model predictions. The electrostriction coefficient M of the composites were also found by measuring the field induced displacement in the unpoled composites using a laser interferometer. M attained a minimum at ?~0.3. Other property of the composites such as the thermal expansion was measured using the thermal mechanical analyzer. The shear modulus and the bulk modulus have also been measured and reported in this study.