PBTIO3 SOL-GEL PROCESS STUDIED BY PB-207-NMR, IR, DTA AND XRD

PbTiO3 film and powder materials have been obtained from a sol prepared at room temperature by mixing lead(II) acetate trihydrate (LAT) and tetraisopropylorthotitanate (TPOT) in methoxyethanol. The sol-gel process was studied by means of Pb-207 nuclear magnetic resonance and infrared spectroscopy, differential thermal analysis and X-ray diffraction measurements. This investigation shows that an interaction between LAT and TPOT occurs immediately on mixing in solution and, as a result of the interaction, the lead and titanium compounds are indistinctly linked together through bidentate acetate bridging. This linkage remains unchanged during solution reactions and gelation, Pb-O-Ti bonding being absent at this stage. Pb-O-Ti bonding in the sol-gel materials is believed to be first formed between 200 and 350 degrees C during the decomposition of the OAc group of LAT and its removal from the gel. The gel retains its amorphous state on heating at 370 degrees C for 1 h. An unidentified primary crystal phase appears after heating the gel at 400 degrees C for 1 h, and it is transformed into perovskite PbTiO3 crystals at 500 degrees C and higher temperatures.