Conductivity and crystallography of new alkali rare-earth silicates synthesized as possible fast-ion conductors

S. M. Haile*, B. J. Wuensch, T. Siegrist, R. A. Laudise

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

Eight potassium neodymium silicates have been synthesized as possible fast-ion conductors. Hydrothermal growth experiments in the high-silica region of the SiO2·H2O·Nd2O3·K2O system yielded crystals of the following phases (five of which are previously unreported) :K3NdSi6O15, K8Nd3Si12O32OH, K10Nd4Si14O39, K4Nd2Si8O21, K3NdSi18O1 9, K12Nd2Si18O45, K5Nd3Si20O47, and KNd9(SiO4)6O2. The compositions and crystallographic data were determined using electron microprobe measurements and precession X-ray photographs, respectively. Single-crystal intensity data for phases K3NdSi6O15 and K8Nd3Si12O32OH were obtained with a four-circle diffractometer. Of these eight phases, six have been obtained as crystals large enough to permit conductivity measurements along at least one crystallographic axis. Conductivities were measured from 300 to 900 °C in an air atmosphere using either complex impedance techniques or single-frequency ac methods. Our results show that activation energies range from 0.3 to 2.2 eV, that the conduction process does not strictly follow the Arrhenius equation, and that these silicates are significantly anisotropic with respect to conductivity. In the K3NdSi6O15 phase this anisotropy corresponds well to expectations based on structural considerations.

Original languageEnglish (US)
Pages (from-to)1292-1301
Number of pages10
JournalSolid State Ionics
Volume53-56
Issue numberPART 2
DOIs
StatePublished - Jan 1 1992

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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