Piezoceramic material with anisotropic graded porosity

Porous PZT ceramics were produced at increasing porosity content to a maximum of 40 vol.%. Anisotropic porosity was obtained by adding lamellar graphite as pore forming agent. The elasto-piezo-dielectric properties of the samples with uniform porosity were correlated to the increasingly higher degree of anisotropy introduced as the total pore volume increases. Higher anisotropy enhances the decoupling of the longitudinal to transverse effect. A piezoelectric bending actuator with functionally graded microstructure (FGM) was produced by stacking layer by layer, in the green state, the PZT powder at increasing graphite content, followed by die pressing and co-firing. The final pore distribution measured across the section and the performance of the porosity graded material arise from the combination of the properties of the homogeneous layers. This makes it possible to precisely tailor the performance of the porosity graded material.