MONOLITHIC CRYSTALLINE LEAD-ZIRCONATE-TITANATE AEROGELS

Stoichiometric lead zirconate titanate (PbZr0.53Ti0.47O3, PZT) alkogel s were prepared by a sol-gel technique. Drying under ambient condition s yielded xerogels while solvent exchange and supercritical drying eit her in carbon dioxide or isopropanol led to highly porous aerogels. A porosity of only 3% can be detected in the amorphous air-dried xerogel s. Gels supercritically dried in carbon dioxide are also amorphous and exhibit a surface area of 323 m(2) g(-1) as determined by nitrogen ad sorption and a porosity of 84%. Neither xerogels nor CO2-dried aerogel s can be transformed into polycrystalline PZT by heat treatment withou t cracking. Aerogels dried in supercritical isopropanol exhibit porosi ties comparable to samples dried in carbon dioxide. XRD and DTA measur ements indicate that during drying, metallic lead is formed as an inte rmediate phase. This type of aerogel can be transformed into poly crys talline PZT with porosities exceeding 70%. These results are compared to previous studies of lead titanate (PT) aerogels. Even though the fi nal porosity of PZT aerogels is smaller than that of the corresponding PT aerogels, their enhanced mechanical stability may prove useful for piezoelectric materials with low acoustic impedances. (C) 1998 Elsevi er Science B.V. All rights reserved.