DENSIFICATION AND CRYSTALLIZATION OF LEAD TITANATE AEROGELS

Crack-free monolithic lead titanate (PbTiO3, or PT) aerogels were prep ared via a sol-gel process and drying in supercritical carbon dioxide. The material was characterized by thermogravimetric analysis, dilatom etry, helium pycnometry, and X-ray diffraction. Skeletal densification was the main reason for the observed shrinkage of the heat-treated po rous material at temperatures <450 degrees C. The transition (at tempe ratures of 500 degrees-600 degrees C) from an amorphous state to the c rystalline (tetragonal) PT was accompanied by significant particle coa rsening, as revealed by transmission electron microscopy. Nitrogen ads orption measurements confirmed that crystallization was preceded by th e formation of interparticle necks.