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.