PHASE-FORMATION AND CHARACTERIZATION OF THE SRBI2TA2O9 LAYERED-PEROVSKITE FERROELECTRIC

The Sr-Bi-Ta-O system is of interest for thin-film non-volatile ferroe lectric memories. A better understanding of the process by which the p erovskite phase forms can provide insight for improved processing of t his ferroelectric compound. We have prepared thin-films by a chemical method using Sr-acetate, Bi-acetate and Ta-ethoxide; cation ratios wer e similar to 1:2:2 for Sr, Bi, and Ta, respectively. Results of in-sit u crystallization studies using High-Temperature Grazing-Incidence X-r ay Diffraction (HTGIXRD) have demonstrated that a fluorite structure, forming in the similar to 600 - 700 degrees C range, acts an intermedi ate phase prior to the crystallization of the perovskite. Additional s amples with cation ratios of similar to 1:0.8:2 were also investigated . Results for samples prepared with the 0.8 Bi content indicated that a pyrochlore phase forms which contains a substantial deficiency in Bi compared to the composition of the perovskite phase. The structures o f the pyrochlore and fluorite phases and their relation to the formati on of the perovskite ferroelectric are discussed.