Abstract
The determination of metal location in zeolite and an estimation of site occupancy by using spherical aberration-corrected scanning transmission electron microscopy ( Cs -corrected STEM) were attempted through the observation of La-exchanged NaY zeolite (LaNaY). LaNaY was prepared by the ion exchange of NaY zeolite and observed using high-angle annular dark-field (HAADF)-STEM. Simultaneous imaging of both the zeolite framework and La atomic columns revealed the La positions to be in sites I and I’. From the averaged HAADF intensity of each La site, the La occupancy was estimated to be about a fourth for both sites I and I’. The estimated La occupancy of site I was much larger than that measured by XRD, suggesting that the STEM data reflects the highly dehydrated state of LaNaY. In addition, methods for observation of individual La atoms are described. • La atoms and T-sites in La-exchanged NaY zeolite were simultaneously visualized. • The locations of La atoms were determined, and the La site occupancy was estimated. • Methods for observing individual La atoms were described.
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