Alessandra Sanson
e-mail: sanson@istec.cnr.it
Edoardo Roncari
Institute of Science and Technology for Ceramics
(ISTEC)-CNR,
Via Granarolo 64,
48018 Faenza (Ravenna), Italy
Stefano Boldrini
Insitute of Biomedical Engineering (ISIB)-CNR,
Corso Stati Uniti 4,
35127 Padua, Italy
Patrizia Mangifesta
Institute of Science and Technology for Ceramics
(ISTEC)-CNR,
Via Granarolo 64,
48018 Faenza (Ravenna), Italy
e-mail: mangifesta@istec.cnr.it
Lioudmila Doubova
Insitute for Energetics and Interphases
(IENI)-CNR,
Corso Stati Uniti 4,
35127 Padua, Italy
Eco-Friendly Screen-Printing Inks
of Gadolinia Doped Ceria
Gadolina doped ceria (GDC) is a promising electrolyte for intermediate temperature
solid oxide fuel cells (IT-SOFC). Dense layers of this material can be economically
deposited by screen printing. However, the inks for this technique generally use organic
compounds that can raise health and safety issues, as well as economical issues. In order
to obtain a low-cost alternative to the generally accepted organic-based ink, four differ-
ent blends of binders were considered to prepare water-based GDC inks. The systems
were deposited onto green NiO/GDC anodes produced by tape casting and treated at
1673 K for 4 h. By choosing the right combination of solvents and binders, it was
possible to obtain a dense crack-free film of GDC from a water-based system.
DOI: 10.1115/1.3120271
1 Introduction
Gadolinia doped ceria Ce
0.8
Gd
0.2
O
2-
, GDC is considered one
of the most promising alternatives to yttria stabilized zirconia
YSZ for application in solid oxide fuel cells SOFCs operating
at intermediate temperatures 1.
The former electrolyte supported SOFCs are nowadays com-
monly replaced by the electrode-supported ones in which a thin-
film electrolyte is deposited onto an electrode, generally the an-
ode. Screen printing offers several advantages over other
techniques for the production of thin electrolyte layers: thickness
control, reproducibility, low cost, and easy applicability to large
scale production 2,3.
The inks used in the screen printing process of SOFC elements
are generally based on terpineol and butyl carbitol acetate 4.
These compounds require the use of chlorinated hydrocarbons ei-
ther as a cosolvent to regulate the viscosity or as a washing me-
dium at the end of the process 4. Furthermore, when printed
substrates are dried in ovens, an explosive atmosphere can be
originated by the air and hydrocarbon mixture leading to safety
issues 5. Therefore, water-based systems are interesting not only
for their low cost and easy handling but also for environmental
reasons. A screen printing ink is a complex nonequilibrium system
that has flow properties strongly related to the properties of its
components ceramic powder but also solvent, dispersant, binder,
and plasticizers. The ink rheology has direct impact on the qual-
ity of the deposition and therefore must be carefully controlled in
order to obtain crack-free films. The ideal ink should have the
proper degree of both pseudoplastic and thixotropic behaviors to
fully accomplish the need of the screen printing process. Because
the rheology of the ink is strongly dependent on the rheology of
the vehicle, the solvent and the binder are two key components in
a screen-printing ink. The former determines the drying rate of the
ink during the printing process, while the selective addition of the
binder can be used to adjust specific flow characteristics, as thix-
otropy and pseudoplastic properties 6.
This paper reports the study on the influence of four different
blend of binders and of the solvents on the rheology of a water-
based GDC ink and on the morphology of the deposited film. The
major drawbacks connected with the water-based system are
linked to the fast evaporation rate of water and the cracks in the
fired film induced by the thickness generally required for the
screen-printing process. The right choice of binders allowed us to
produce a dense and crack-free GDC layer onto a GDC/NiO an-
ode after firing at 1673 K for 4 h from an eco-friendly water-based
GDC ink. To the authors’ knowledge, this is the first time in which
a water-based ink for the deposition of SOFC film is presented.
2 Experimental
Commercially available gadolinia doped ceria Ce
0.8
Gd
0.2
O
2-
powder GDCPraxair, USA with specific surface area of
5.2 m
2
/ g was used as a starting material. Distilled water and 1.2
propylene glycol PGRiedel de Haën, Germany were consid-
ered as solvents, whereas polyvinyl alcohol PVAFluka, Swit-
zerland, polyvinyl pyrrolidone PVPFluka, sodium alginate
AlgFluka, hydroxyethylmethy cellulose MHECAqualon,
USA, and carboxmethylcellulose CMCTylose, USA were
chosen as binders. The ink composition included also a dispersant,
an antifoam, and a plasticizer. All the inks were prepared varying
the nature of the binder only, while the powder loading and the
nature and quantity of the dispersant, antifoam, and plasticizer
were kept constant. The ink formulation was chosen according to
what was already optimized in organic media a powder loading
of 55 wt %. After a preliminary step in the agate mortar, the
as-prepared ink was milled in a three-roll mill equipped with zir-
conia rollers of nanometric finishing Exakt 80E, Exakt, Ger-
Manuscript received February 1, 2008; final manuscript received March 3, 2009;
published online July 19, 2010. Review conducted by Stefano Ubertini. Paper pre-
sented at the Second European Fuel Cell Technology and Applications Conference
EFC2007, Rome, Italy, December 11–14, 2007.
Journal of Fuel Cell Science and Technology OCTOBER 2010, Vol. 7 / 051013-1
Copyright © 2010 by ASME
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