Raman spectroscopic fingerprint of ferroelectric SrBi₂Ta₂O₉ thin films: A rapid distinction method for fluorite and pyrochlore phases

We present the use of Raman spectroscopy as a rapid and sensitive means for the phase characterization of ferroelectric SrBi₂(Ta_1-xNb_x)₂O₉ (SBTN) thin films. It is shown that frequency shifts, together with Raman selection rules, are characteristic of layered perovskite, fluorite and pyrochlore structures, and thus the Raman spectra can be used as a fingerprint of the symmetry of the examined film. We also find the enormous potential of Raman spectroscopy to detect and quantify fractions of the fluorite and pyrochlore phases coexistent with the SBTN phase.