Synthesis of ferroelectric nanocrystalline SrBi2Ta2O9 powder by the colloid-gel process

An innovative colloid-gel process using inorganic salts as starting materials has been successfully developed for preparing ferroelectric strontium bismuth tantalate (SrBi2Ta2O9) powder. This new technique began with the preparation of a mixture of Ta(OH)5 colloid with the aqueous solutions of strontium and bismuth cations, followed by the addition of ethylene glycol and citric acid as gel-forming reagents. During the calcination process the fluorite phase was formed as an intermediate that was subsequently converted into the SrBi2Ta2O9 phase. After calcination at 750°C, pure ultrafine SrBi2Ta2O9 polycrystalline powder with a narrow particle size distribution was obtained. The primary particle size of the obtained SrBi2Ta2O9 powder was around 40 nm. In comparison with the solid-state reaction, the newly developed colloid-gel process significantly reduces the heating temperature for synthesizing SrBi2Ta2O9, as well as the particle size of the obtained powder.