Piezoelectric and dielectric properties of PZT/PVC and graphite doped with PZT/PVC composites

The PZT/polyvinyl chloride (PVC) composites are prepared by hot-pressing technique using a novel nanocrystalline PVC. The d33 value observed in this work for the 0.5PZT/0.5PVC composite is close to the 0.5PZT/0.5PVDF composite reported in the literature, but PVC is much cheaper than PVDF. The three-phase fgC/0.5PZT/(0.5 - fg)PVC composites are obtained by adding a small content of graphite particles to the 0.5PZT/0.5PVC composite. The measured dielectric properties demonstrate that a percolation transition occurs in the three-phase composites as in normal two-phase metal-insulator continuum media. An optimum piezoelectric property is obtained by adding fg = 0.005 before the percolation threshold in the fgC/0.5PZT/(0.5 - fg)PVC composites, which is 50% higher than that of the 0.5PZT/0.5PVC composite. X-ray powder diffraction (XRD) patterns show domain rotation is easy in this three-phase composite, and P-E hysteresis loops conform that a small amount of graphite particles adding in the composite break the polymer seclusion, and considerably decrease coercive field of the composite.