Electrical properties of PZT aerogels

PZT aerogels are prepared by sol-gel processing and subsequent supercritical drying. After sintering of the highly porous and uncalcined green body for up to 16 h in the temperature interval from 650 to 950 degreesC, a porous ceramic with a perovskitic PZT backbone is obtained. These PZT aerogels were characterized in terms of a possible application as ultrasound transducers. Samples were sintered in the temperature range between 650 and 950 degreesC and their elastic modulus was determined. Dielectric permittivities and dielectric charge constants were measured. the results can be interpreted with respect to the porosity and surface area of the samples. The electrical resistance of PZT aerogels is low compared to bulk material, a significant contribution of surface layer conductivity could be determined. The resulting low electrical breakdown field strengths hinder polarization. Additionally the inhomogeneous distribution and small strength of local poling fields has to be considered. Nevertheless dielectric hysteresis loops were obtained for samples annealed at 850 and 950 degreesC, respectively. (C) 2002 Elsevier Science Ltd. All rights reserved.