Characterization of porous piezoelectric ceramics: The length expander case

Porous piezoelectric ceramics and 0–3/3–3 connectivity piezoelectric composites are normally characterized following the Standards on Piezoelectricity. Nevertheless, these materials are not homogeneous and losses are significant. New constitutive and wave equations have been obtained recently for these kind of materials. The objective of this paper is to derive new definitions for the electromechanical coupling coefficients and a suitable characterization procedure according to the new constitutive and wave equations previously mentioned. In particular, the case of the length expander bar mode is analyzed in detail. The study of resonant elements requires the use of suitable boundary conditions. In this case the boundary conditions are borrowed from the theory of poroelasticity and extended for a piezoelectric material. Finally the procedure is applied to characterize a commercial porous piezoelectric ceramic.