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Published October 2000 | Published
Journal Article Open

X-ray diffraction study of K_3NdSi_7O_(17): a new framework silicate with a linear Si-O-Si bond

Abstract

Hydrothermal investigations in the high-silica region of the K_2O-Nd_2O_3-SiO_2 system, carried out in a search for novel fast-ion conductors (FICs), yielded the new compound tripotassium neodymium heptasilicate, K_3NdSi_7O_(17). Single-crystal X-ray methods revealed that K_3NdSi_7O_(17) crystallizes in space group P\bar 3, has lattice constants a = 16.131 (2) and c = 7.7146 (19) Å, Z = 4, and 22 atoms in the asymmetric unit. Refinement was carried out to a residual, R(F), of 0.0253 and a weighted residual, wR(F^2), of 0.0702 using anisotropic displacement parameters for all atoms. The silicate anion forms an interrupted framework, within which both Nd octahedra and K polyhedra are situated. The structure is unusual in that it contains a symmetry-constrained Si-O-Si bond angle of 180°. No isomorphs to K_3NdSi_7O_(17) are known.

Additional Information

Copyright © 2000 International Union of Crystallography. Received 20 December 1999. Accepted 3 May 2000. The authors are grateful to Karl Peters of the Max-Planck-Institut für Festkörperforschung for collecting single-crystal intensity data and aiding with the structure determination. Steve Recca and Mike Jercinovic of the Massachusetts Institute of Technology kindly carried out microprobe analyses. SMH thanks Joachim Maier for hosting her visit to MPI where some portions of this research were carried out. This work is dedicated to the memory of the late Robert A. Laudise, in whose laboratory the hydrothermal syntheses were carried out.

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August 21, 2023
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