SAXS investigation of morphology changes in lead-titanate aerogels

Highly porous lead-titanate (PT) aerogels were prepared by sol-gel-processing and drying under supercritical conditions in isopropanol. After annealing in air for one hour at seven temperatures from 110 to 600 degrees C samples were ground for SAXS-measurements. Different models were used to fit the scattering data. Nanosized structures in the PT-aerogel backbone vanish upon thermal treatment around 250 degrees C. The specific surface area decreases monotonically with annealing temperature. SAXS-data are compared to recent N-2-sorption measurements. The main finding of our investigations was that the crystallization of small amorphous spheres into big angular particles can be studied using a concept called angulosity. (C) 1998 Elsevier Science B.V. All rights reserved.