Sodium intercalation into then= 2 Ruddlesden?Popper type host Y2Ti2O5S2: synthesis, structure, and properties of ?-NaxY2Ti2O5S2(0

Clarke, Simon J., Denis, Sophie G., Rutt, Oliver J., Hill, Timothy L., Hayward, Michael A., Hyett, Geoffrey and Gál, Zoltán A. (2003) Sodium intercalation into then= 2 Ruddlesden?Popper type host Y2Ti2O5S2: synthesis, structure, and properties of ?-NaxY2Ti2O5S2(0. Chemistry of Materials, 15 (26), 5065-5072. (doi:10.1021/cm034762f).

Abstract

Sodium intercalation into the oxide slabs of the cation-deficient n = 2 Ruddlesden-Popper oxysulfide Y2Ti2O5S2 to produce alpha-NaxY2Ti2O5S2 (0 < x less than or equal to 1.0) is reported. These materials have been probed as a function of the amount of intercalated sodium using high-resolution neutron powder diffraction. At all levels of sodium intercalation the tetragonal symmetry of the host is retained, for example: Na0.35(5)Y2Ti2O5S2, I4/mmm, a = 3.80171(2) Angstrom, c = 22.6270(2) Angstrom, Z = 2; Na0.84(2)Y2Ti2O5S2, I4/mmm, a = 3.84429(6) Angstrom, c = 22.5440(4) Angstrom, Z = 2 at 298 K. The sodium ion occupies a site coordinated by twelve oxide ions which corresponds to the "A"-site in the perovskite-like oxide slabs of the structure. At levels of sodium intercalation up to the maximum alpha-Na1.0Y2Ti2O5S2 the cell volume increases approximately linearly with x as electrons enter bands which are antibonding with respect to the Ti-O framework. The effects on the structural details of electrostatic repulsion between the yttrium and intercalated sodium ions is discussed, and these materials are compared with the analogous lithium intercalates. Magnetic susceptibility and electrical resistivity measurements are consistent with delocalization of the intercalated electrons especially for large x. The insertion of lithium into alpha-Na0.5Y2Ti2O5S2 and of magnesium into Y2Ti2O5S2 are also reported.

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Contributors

Author: Geoffrey Hyett

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