CERAMIC POWDER-POLYMER PIEZOCOMPOSITES FOR ELECTROACOUSTIC TRANSDUCTION - MODELING AND DESIGN

A measurable piezoelectric response in loaded ceramic powder-polymer p iezocomposites requires a certain degree of connectivity among the ind ividual ceramic grains, so that the spatial connectivity of the compos ite can be located somewhere between the ideal (0-3) and (3-3) connect ivity 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 th eoretical approach, recently developed to study porous piezoelectric c eramics, is applied to assess the properties of such composite materia ls. In addition, previous approaches are reviewed. Two different ceram ic materials and polymers are used to produce composite materials foll owing different fabrication routes. The samples are characterized foll owing the new approach, paying special attention to the determination of the real spatial connectivity of the composites, the bounding betwe en 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.