Ferroelectric ceramic-plastic composites for piezoelectric and pyroelectric applications

Abstract

Abstract Consideration of the influence of crystal symmetry, macrosymmetry, and inter-phase connectivity have been used to explore possible macrostructures of interest as piezoelectric or pyroelectric composites. Based on these design considerations, ceramic-plastic composites have been fabricated with 3–3 phase connectivity by the replication of natural template structures such as coral. Composites prepared in this way have piezoelectric 933 and 9h coefficients more than an order of magnitude higher than the coefficients of the homogeneously poled ferroelectric ceramic. Large voltage coefficients were also obtained from 3–1 piezoelectric composites made by embedding PZT fiber arrays in epoxy cement. Processing methods are described for producing straight and helical piezoelectric fibers by both extrusion and casting of PZT slips. Pyroelectric measurements on ceramic-plastic composites led to two interesting results: thermal expansion mismatch between the two phases can couple to the piezoelectric coefficients to give a large secondary pyroelectric effect, and, secondly, boracite-plastic composites have extremely large voltage coefficients (p/ϵ), comparable to boracite single crystals and the very best vidicon materials.