Preparation of SrBi2Ta2O9 from Metal Alkoxides

SrBi2Ta2O9 (SBT) has potential application in FERAM. Some problems in the sol-gel processing of SBT, such as the solubility of metal alkoxides, chemical modification with a chelating reagent and crystallization behavior of the gels, are investigated.The starting solutions were prepared with Sr(OC4H9)2, Bi(OC3H7)3, and Ta(OC2H5)5. Ethoxyethanol and acetylacetone (ACAC) were used as solvent and chelating reagent, respectively. Ta- and Bi-alkoxide are chemically modified with ACAC, but Sr-alkoxide was not. The SBT solution was stabilized with ACAC for ca. 3 months. After hydrolysis of the SBT solution with the addition of ACAC, a monolithic and transparent gel was obtained at room temperature in 100 days. The X-ray diffraction peaks of SBT and very weak peaks of SrTa2O6 (ST) and SrBi2O4 (SB) were found after calcination at 700°C for both of the gels obtained with and without addition of ACAC. In contrast, the stronger peaks of ST and SB were observed for the powder mixture of SrCO3, Bi2O3, and Ta2O5 after calcination at 800°C. These results show the better homogeneity of the gels.