International Journal of Minerals, Metallurgy and Materials
Volume 19, Number 9, Sep 2012, Page 863
DOI: 10.1007/s12613-012-0640-0
Corresponding author: Ismunandar, E-mail: ismu@chem.itb.ac.id; Fitria Rahmawati, E-mail: fitria@uns.ac.id
© University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg 2012
SOFC composite electrolyte based on LSGM-8282 and zirconia or doped
zirconia from zircon concentrate
Fitria Rahmawati
1,2)
, Bambang Prijamboedi
1)
, Syoni Soepriyanto
3)
, and Ismunandar
1)
1) Inorganic and Physical Chemistry Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha 10 Bandung 40132, Indonesia
2) Research Group of Solid State & Catalysis, Chemistry Department, Sebelas Maret University, Jl. Ir. Sutami 36 A Kentingan Surakarta 57126, Indonesia
3) Metallurgical Engineering Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Jl. Ganesha 10 Bandung 40132, Indonesia
(Received: 18 July 2011; revised: 10 October 2011; accepted: 6 November 2011)
Abstract: The aim of this research is to study zirconia-based electrolyte materials to increase the commercial value of zircon concentrate as a
side product of tin mining industries. Synthesis of CaO-Y
2
O
3
-ZrO
2
(CYZ) and 8mol% Y
2
O
3
-ZrO
2
(8YSZ) was carried out by solid state re-
action. The result shows that ZrO
2
presents in tetragonal phase. Doping of Y
2
O
3
into ZrO
2
allows a phase transformation from tetragonal into
cubic structure with small percentage of monoclinic phase. Meanwhile, doping of CaO-Y
2
O
3
allows a phase transformation into a single cu-
bic phase. These phase transformations enhance the ionic conductivity of the material. Introduction of 10wt% of LSGM-8282 into CYZ
(CYZ-L90:10) allows further improvement of inter-grain contact shown by SEM morphological analysis and leads to the enhancement of
ionic conductivity.
Keywords: solid oxide fuel cells (SOFC); solid electrolytes; LSGM electrolyte; zirconia; phase transformations; ionic conductivity
1. Introduction
The electrolyte material of yttria-stabilized zirconia (YSZ)
has been extensively investigated during the last decade, and
it is widely used in solid oxide fuel cells (SOFC) [1-3],
which operate in the high temperature region of 850-1000°C.
For the system of high temperature solid oxide fuel cells
(HT-SOFCs), enormously high efficiencies can be achieved
by its integration with a gas turbine for large-scale stationary
applications [4]. Large HT-SOFC systems must be built in
the stacking structure and they need various ceramics and
high-temperature metal alloys, limiting the choice of mate-
rials. HT-SOFCs also face the problem of high corrosion
rate of stacks. Therefore, for the reduction in cost and corro-
sion rate, there is always a demand to reduce the operating
temperature of SOFC. Thus, any incremental improvement
in the ionic conductivity of the electrolyte is meaningful for
applications [5].
A considerable interest in the mixed dopant effect on the
ionic conductivity in several ternary systems containing
ZrO
2
and Y
2
O
3
has arisen. These ternary systems have been
studied from the viewpoint of structural and electrical prop-
erties. Oxides commonly used as the third component were
calcia [6-8] or magnesia [9]. The mixed CaO/Y
2
O
3
-stabi-
lized ZrO
2
(CYZ) exhibits comparable ionic conductivity to
YSZ even at the operating temperature around 1000°C. This
implies that the ternary system of ZrO
2
-Y
2
O
3
-CaO may be
more attractive than other ternary systems, mainly because
of the lower cost of CaO compared to other trivalent oxides
such as Sc
2
O
3
[10] and Yb
2
O
3
[11]. Bućko [12] has synthe-
sized CYZ using the hydrothermal method from
co-precipitated zirconia hydrogel and found that the fully
cubic phase could be obtained after sintering at 1300°C. It
has also been found that the substitution of calcia for yttria
as well as yttria for calcia in the zirconia solid solutions led
to an enhancement of ionic conductivity. In particular, for a
sample with 8mol% oxygen vacancies (8C10Y90, the mass
ratio of CaO:Y
2
O
3
is 10:90), substitution of yttria for calcia
caused a significant enhancement of bulk conductivity and
grain boundary conductivity.