THERMAL-DECOMPOSITION OF (SR, TI) ORGANIC PRECURSORS DURING THE PECHINI PROCESS

The evolution of (Sr, Ti) resin intermediates from the solutions during the Pechini process, and their pyrolysis to SrTiO3 were investigated using differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction techniques. In order to understand the Pechini process better, the organic solutions containing either only titanium ions or no metal ions were also prepared and thermally polymerized so that their decomposition processes could be examined in the same manner. In the case of the initial (Sr, Ti) organic solutions, all organic acid groups were bonded mainly either with ethylene glycol forming esters, or with Sr/Ti ions forming unidentate complexes. With heat treatment, the nature of the bonding between carboxylate groups and Sr/Ti ions changed: unidentate → bridging → ionic. Carbonate species were detected at 530 ° C using infrared spectra. Their concentration was reduced as SrTiO3 formed. On the basis of powder X-ray diffraction data, it is doubtful that SrC03 and TiO2 were formed as distinct intermediate phases. Possibly, a carboxylate complex (Sr2Ti2O5CO3) was formed prior to the formation of SrTiO3. © 1990 Chapman and Hall Ltd.