Preparation of monolithic crystalline lead titanate aerogels

Lead titanate gels were prepared via sol–gel synthesis and dried either in supercritical carbon dioxide or isopropanol. Both types of aerogels were characterized by means of thermal analysis and transmission electron microscopy. Helium pycnometry and nitrogen adsorption measurements were performed on samples that had been annealed at temperatures up to 600°C. Phase transformations and the crystallization of tetragonal PbTiO3 were monitored by X-ray diffraction. While aerogels supercritically dried in carbon dioxide disintegrate upon heat treatment, samples dried in isopropanol can be transformed to the crystalline state as monoliths. With an envelope density of 0.75 g cm-3 these ceramics exhibit a porosity of 90%. © 1998 Chapman & Hall