Ceramic powder-polymer piezocomposites for electroacoustic transduction: modeling and design

A measurable piezoelectric response in loaded ceramic powder-polymer piezocomposites requires a certain degree of connectivity among the individual ceramic grains, so that the spatial connectivity of the composite can be located somewhere between the ideal (0-3) and (3-3) connectivity limits. This non-zero spatial connectivity of the ceramic grains in the polymer matrix makes the use of classical theoretical methods to assess dielectric and mechanical properties difficult, since these are mainly based on scattering or averaging approaches. Here, a new theoretical approach, recently developed to study porous piezoelectric ceramics, is applied to assess the properties of such composite materials. In addition, previous approaches are reviewed. Two different ceramic materials and polymers are used to produce composite materials following different fabrication routes. The samples are characterized following the new approach, paying special attention to the determination of the real spatial connectivity of the composites, the bounding between ceramic grains and polymer, and the degree of poling. As a result, a comprehensive characterization route for these materials is proposed. (C) 1998 Elsevier Science B.V. All rights reserved.