RAMAN-SPECTROSCOPIC STUDY OF THE FORMATION OF BARIUM-TITANATE FROM AN OXALATE PRECURSOR

Barium titanyl oxalate (BaTiO(C2O4)2) is used commercially as a precursor for the preparation of the ferroelectric ceramic BaTiO3. This study examines the conversion of this mixed oxalate compound to BaTiO3 upon thermal treatment. The molecular structure of the mixed oxalate has been determined by Raman spectroscopy to consist of a Ti4O4 ring, in contrast with the earlier reports that this molecule contains a titanyl (Ti=0) unit. The mixed oxalate was heated from room temperature to 800-degrees-C, and the structural changes that occurred were followed by Raman spectroscopy at ambient temperature. As a function of temperature, the bidentate oxalate ligand changes to a bridged oxalate, followed by decomposition to ligated carbonate and then to ionic carbonate. All traces of the ligand disappear beyond 800-degrees-C. The intermediate that exists in the temperature range 250-600-degrees-C is a Ba-Ti amorphous complex. BaTiO3 first appears at 580-degrees-C. The organic ligand serves to provide an atomic level contact between the metal ions, thus providing a route to BaTiO3 formation at lower temperatures.