Synthesis and characterization of nanosized SrBi₂Ta₂O₉ powder by a novel sol-gel process

Chemically homogeneous SrBi₂Ta₂O₉ (SBT) sol was synthesized using ethoxy tantalum, strontium acetate, and bismuth subnitrate as starting materials, methoxyethylene as a solvent and acetic acid (HOAc) as a catalyst. Single-phased perovskite phase SBT ferroelectric ultrafine powder was obtained after the dried gel was treated at 350°C for 30min and calcined at 800°C for 1h. FT-IR, XRD, TEM and TG-DTA were employed to investigate the transformation processes of sol to gel and gel to ultrafine SBT powder. Acetic acid not only acts as an acid catalyst, but also changes the alkoxide precursor as a ligand at a molecular level. Bidentate acetates replace OR groups and are directly bounded to the tantalum, leading to the formation of Ta (OR)_x(OAc)_5-x. The perovskite SBT phase formed via intermediate phase Bi₃TaO₇ and a Bi-deficient pyrocholore phase.