TOPOTACTIC H
/Li
ION EXCHANGE ON La
2/3x
Li
3x
TiO
3
: NEW
METASTABLE PEROVSKITE PHASES La
2/3x
TiO
33x
(OH)
3x
AND
La
2/3x
TiO
33x/2
OBTAINED BY FURTHER DEHYDRATION
N.S.P. Bhuvanesh
1
, O. Bohnke ´
1
, H. Duroy
1
, M.P. Crosnier-Lopez
1
, J. Emery
2
, and
J.L. Fourquet
1
*
1
Laboratoire des Fluorures (UPRESA 6010, CNRS);
2
Laboratoire de Physique de l’Etat Condense ´ (UPRESA 6087, CNRS), Faculte ´ des
Sciences du Mans, Universite ´ du Maine, Avenue O. Messiaen, 72085 Le Mans Cedex 9,
France
(Refereed)
(Received February 23, 1998; Accepted March 23, 1998)
ABSTRACT
We have synthesized novel La
2/3-x
TiO
3-3x
(OH)
3x
(0.07 x 0.13) com-
pounds by ion exchange of the lithium ions from La
2/3-x
Li
3x
TiO
3
in dilute
HNO
3
at 60°C. The proton derivatives crystallize in tetragonal perovskite
cells (a a
p
, c 2a
p
) similar to those of the parent oxides. Interestingly, the
protonated oxides (characterized by X-ray diffraction (XRD), thermogravi-
metric analysis (TGA), and
1
H nuclear magnetic resonance (NMR) yield new
metastable A-site- and oxygen-deficient perovskites La
2/3-x
TiO
3-3x/2
at
about 800°C. © 1998 Elsevier Science Ltd
KEYWORDS: A. oxides, B. chemical synthesis, C. X-ray diffraction, D.
defects, D. ionic conductivity
INTRODUCTION
The lithium lanthanum titanates of the series La
2/3-x
Li
3x
TiO
3
(LLTO) have received a
considerable attention in recent years [1– 4], in view of interest in their structure [3-8] and
high lithium ion conduction [1,2,9,10]. A maximum value of conductivity, = 3.9 10
-4
Scm
-1
at 300 K has been reported [10] for the composition with x = 0.10. These oxides
*To whom correspondence should be addressed.
Materials Research Bulletin, Vol. 33, No. 11, pp. 1681–1691, 1998
Copyright © 1998 Elsevier Science Ltd
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