e
e
δ
S. Bošković
1,a
, D. Djurović
1
, B. Matović
1
, M. Čančarević
1
,
Z. DohčevićMitrović
2
, Z. Popović
2
, M. Zinkevich
3
and F. Aldinger
3
1
Vinča Institute of Nuclear Sciences, Belgrade
2
Institute of Physics, Zemun, Serbia and Montenegro
3
MaxPlanck Institute für Metallforschung, Stuttgart, Germany
a
boskovic@vin.bg.ac.yu
: Ceria Nanopowders, Properties, Reaction Synthesis, SOFC.
Abstract. One of the methods for powder synthesis that is both cost and time effective is the self
propagating room temperature synthesis. We applied this method to synthesize rare earth doped
ceria nanopowders. Since they exhibit very high ionic conductivity at intermediate temperatures
these compositions are attractive for a new generation of nanostructured ceramics applicable in
solid oxide fuel cells as electrolytes. In this paper we paid our attention to the reaction based on
methathetical pathway, whereby solid solution nanopowders of rare earth elements with ceria were
obtained at room temperature. Compositions of Ce
1x
Re
x
O
2δ
(Re = Y , Nd) were synthesized with x
ranging from 0 to 0.20. The reaction course is discussed and the properties of the obtained powders
are presented.
Introduction
Ceria has attracted much attention recently, because of many interesting properties. It is used as
mechanical polishing medium, additive to other hightech ceramics, automobile exhaust catalyst,
radionuclide absorber from water, etc. It is however very important component electrolyte in
future solid oxide fuel cells, because of its higher ionic conductivity at lower temperatures than that
of nowadaysused materials. For all these applications, nanometric size powders are advantageous.
Namely, it is known that the sintering temperature decreases when nanosized powders are used. On
the other hand, referring to SOFC, the conductivity in the nanocrystalline grain boundary regions is
greater than for larger grains [1]. In this respect it is important to develop powders of high quality
with particle size in the nanometric range.
One of the methods that is cost and time effective is the selfpropagating room temperature
synthesis of powders. Many of such reactions need to be performed at elevated temperatures to start
propagating [2]. These reactions afterwards develop spontaneously terminating extremely fast.
According to the literature data [3] synthesis of pure ceria was performed by the selfpropagating
method at room temperature. Ceria solid solutions were obtained by this method for the first time
[4]. In this paper the results on the selfpropagating reaction study are presented. Ce
1x
Re
x
O
2δ
solid
solutions of fluorite type, containing Y
3+
and Nd
3+
cations, in the range of 0≤x≤0.20, were
synthesized. Properties of the produced powders are given, too.
Experimental Procedure
For experimental work cerium and dopant ion nitrates were used in the reaction with sodium
hydroxide. The used nitrates were all in the form of hexahydrates. The compositions of the starting
reacting mixtures were calculated according to the nominal composition of the final reaction
product. The calculated fractions of chemicals were hand mixed in an alumina mortar with an
alumina pestle. The mixing took about 57 minutes. Reaction development could be observed by
naked eyes. Immediately after mixing started, liquid appeared followed by the formation of very
thick slurry. This enabled very close contacts between reactants. As soon as mixing became harder,
while the sample was getting dry, it was stopped. After drying at room temperature in the air, the
Materials Science Forum Vol. 518 (2006) pp. 95-100
online at http://www.scientific.net
© (2006) Trans Tech Publications, Switzerland
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the
written permission of the publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net . (ID: 147.91.1.43-04/10/06,12:35:47)