Solid polymer electrolyte and its composites with functional ceramics

Abstract

Composite films consisting of lead zirconate titanate (PZT) inclusions dispersed in the polymer electrolyte polyethylene oxide (PEO) were prepared. Their piezoelectric coefficients d33 and pyroelectric coefficients p were measured. It is found that both coefficients are increased almost proportional to the volume fraction of the ferroelectric ceramic phase. For a 34% PZT composite, d33 and p are 170 pC/N and 120 uC/m2K respectively. The d33 is 7 times higher than the PZT/polyvinylidene fluoride (PVDF) composite and p is 30% higher than that of the PZT/polyurethane (PU) composite with similar ceramics content. It is believed that the enhancement is same as the PZT/PU, which is due to the high electrical conductivity of polymer electrolyte matrix. The conductive matrix helps stabilizing the poled PZT, and on the other hand, enhances amount of induced current between electrodes. Moreover, comparing with hours of poling procedure of ordinary ferroelectric/polymer composites, the poling time of PZT/PEO composites is reduced to the order of few minutes. This is also the advantage of choosing a conductive matrix. These results are confirmed by the theoretical models which take the conductivity of matrix into consideration. In addition to the high piezoelectric and pyroelectric activities of PZT/PEO composites, the magnetoelectric effects of the 3-phase composites with PEO matrix were also investigated. The composites, which are in 0-0-3 connectivity consisted of Terfenol-D particles and PZT particles blended in the PEO matrices. As an a.c. magnetic field applied to the samples, the induced electrical charges flow in external circuit under short circuit condition was measured. The piezoelectric PZT induced the surface charges while it was stressed by the magnetostrictive Terfenol-D as a result of the changing magnetic field. Compared with the samples with poly(methyl methacrylate) (PMMA) matrix, the magnetoelectric signals of the samples with PEO matrix are found to be greater. While samples of LiClO4 doped PEO matrix exhibit the largest magnetoelectric signals. These results show that the large magnetoelectric signals should be attributed to the high ionic conductivity of the polymer electrolyte PEO.