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Home  >  Journal list  >  Journal of the Ceramic Society of Japan  >  Vol.116  No.1355 (July) (2008)  >  pp.803-806

Journal of the Ceramic Society of Japan
<<Previous article Vol.116  No.1355 (July) (2008)   pp.803 - 806 Next article>>

Ionic conductivity of LixLa10-x(SiO4)6O3-x sinters

Naoki TAKEDA1), Yoshiteru ITAGAKI1) and Yoshihiko SADAOKA1)
1) Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University

  A series of Li2O-La2O3-SiO2 sinters were prepared with the various ratios of the associated elements, Li: La: Si = x: (10-x): 6, and their ionic conductivities were examined. All the sinters were mainly composed of the apatite-type LixLa10-x(SiO4)6O3-x crystalline phases but sub-phases were produced in some cases. The lattice parameters of the main phase decreased with an increase in the Li-content, x, up to x = 2.0 and became constant above x = 2.0, indicating that La 4f-site was partially replaced by Li up to the maximum of x = 2.0. The conductivity of the sinters gradually increased with an increase in x to 1.5, but it suddenly dropped down at x = 2.0 and increased again by a further increase in x. The XRD and 29Si-NMR results suggested that the first conductivity increase was due to the decrease in the content of the La2SiO5 sub-phase with the Li replacement. Furthermore, the 7Li-NMR measurements gave evidence that lithium silicate sub-phase was formed at above x = 2 in the grain-boundary of the crystalline phase as a high Li-ionic conducting phase. The Nernst's EMF response of the O2 and CO2 concentration cells suggested that the main ionic carriers were oxide ion at x < 2.0 and lithium ion at x ≥ 2.


Keyword:
Lithium lanthanum silicate, Apatite-type crystal, Iionic conductor, 7Li-NMR, 29Si-NMR, XRD

Received: January 10, 2008
Accepted: May 15, 2008 , Published online: July 01, 2008
Copyright (c) 2008 The Ceramic Society of Japan

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