METHOD OF DISTINGUISHING SrBi2Ta2O9 PHASE FROM FLUORITE PHASE USING X-RAY DIFFRACTION RECIPROCAL SPACE MAPPING

In the Sr-Bi-Ta-Nb-O system, three crystallographic phases are known to exist: the SrBi2(Ta1-xNbx)O9 (SBTN) perovskite, fluorite and pyrochlore phases. The fluorite phase is a low-temperature phase of SBT, which tends to grow in excess Bi compositions, and the pyrochlore phase tends to grow in Bi-deficient compositions. In conventional XRD characterization, the SBTN phase shows strong (115) diffraction around 29. Unfortunately, the other two phases also show their (111) and (222) diffractions near the same angle when the film is prepared on a Pt-coated Si substrate. Therefore, the phase identification of the SBTN phase from the other two phases is almost impossible by the conventional technique. Authors employed XRD reciprocal space mapping to distinguish these phases in the present study. The three crystallographic phases were identified and distinguished from each other. It is ascertained that this technique is effective to identify crystallographic phases especially in the case in which more than two phases show similar diffraction angles. 19 refs.