The influence of internal voids with 3–1 connectivity on the properties of piezoelectric ceramics prepared by a new planar process

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Abstract
Using resonance measurements, the material properties of lead zirconate titanate samples with evenly spaced (anisotropic) internal voids were investigated. Ceramic/air-composites with 3–1 connectivity (0–15% voids) were produced using a new multilayer method. Essential to this new technique is a combination of photolithography with a stacking and pressing step of thin ceramic sheets. The results prove that the permittivity ε, the mechanical quality factor Q t , the frequency constant in thickness direction N t , and therefore also the acoustical impedance Z of the investigated composites decrease greatly with increasing ratio of voids to bulk. The piezoelectric coupling k 32 perpendicular to the internal voids also decreases strongly. The coupling factors parallel to the voids k 31 and in thickness direction kt do not change from those of bulk material. The measurements are compared with calculations which were done using a simple model.