The Structure and Conductivity of K8Nd3Si12O32(OH): A Layered Silicate with Paths for Possible Fast-Ion Condution

S. M. Haile*, B. J. Wuensch, T. Siegrist

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Hydrothermally grown crystals of K8Nd3Si12O32(OH) have been examined by single crystal X-ray methods. The compound crystallizes in space group P1 and has lattice constants a = 6.9660(6) Å, b = 11.4550(10) Å, c = 11.6670(10) Å, α = 87.677(8), β = 87.491(9), γ = 79.083(8). There are 29 nonhydrogen atoms in the asymmetric unit. With one formula unit per unit cell, the calculated density is 2.929 Mg m-3. Refinement was carried out with 5667 independent and significant [I ≥ 2.5σ(I)] structure factors to a residual, R(F), of 0.047 (RW(F) = 0.057) using anisotropic temperature factors for all atoms. The structure, closely related to that of K8Yb3Si12O32(OH), is based on unusually flat Si12O32 layers that are connected by Nd octahedra to form a three-dimensional framework. The silicate layer contains two types of six-membered rings, an eight-membered ring, and a meandering twelve-membered ring. It can be generated from a condensation of wollastonite-type chains and contains structural features found in the "ideal" silicate layers of α-K3NdSi6O15·2H2O and β-K3NdSi6O15. Potassium ions are located in the interstitial sites of the neodymia-silica framework, in channels that run between silicate layers; hydroxyl groups reside within channels that run through the layers. The conductivity in the [0 1 0] direction is given by σ = [1.4×103 K/Ω/T]×exp(-0.8eV/kbT). Charge transport appears to occur by the motion of OH- ions.

Original languageEnglish (US)
Pages (from-to)406-418
Number of pages13
JournalJournal of Solid State Chemistry
Volume148
Issue number2
DOIs
StatePublished - Dec 1999

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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