Atomic environment of tantalum in the intermediate fluorite phase of SrBi₂Ta₂O₉thin films

The intermediate phase involved in the production of ferroelectric material SrBi2Ta2O9 has a fluorite structure. If the structure of the intermediate phase were ideal, all the metal ions would have identical cubic oxygen environments. However, the tantalum ions are much smaller than the strontium and bismuth ions which could result in local deviations from the original structure. We present results of X-ray absorption spectroscopy studies which indicate the local tantalum atomic environments for the intermediate fluorite phase and the ferroelectric final Aurivillius phase material, a layer-structure perovskite. For both phases NEXAFS studies indicated very similar electronic structures at the tantalum sites. The EXAFS analysis revealed local structural information and indicated that the intermediate phase has a defect fluorite structure with the oxygen environment for the tantalum being related to that of the TaO6 octahedra of the final phase material.