APPLICATION CHALLENGES
Both sample mounting methods are placed inside Figure 3 Two probes in
the 2.5mm deep ceramic sample cup so that the contact with the
sample is heated from underneath as well as from sample which is
the sides. The electrical measurements were made mounted in the hot
using a Suss Microtec SOM4 probe station. Probes stage
were attached directly to the sample as it was
heated to temperatures up to 1000
0
C.
The goal for the development is to reduce
operating temperatures from the 800-1000?C
range to as low as 400
0
C while retaining high
performance in the electrodes as this will improve
the overall power output. The measurements made
record changes in impedance as a function of Figure 4 Electrode
temperature and this is directly related to the conductance plot
performance and, ultimately, efficiency.
Using impedance spectroscopy, the performance
of the electrolyte and the electrodes may be
independently studied. In particular, the
performance of the electrodes is crucial to the
efficiency of micro-solid oxide fuel cells. An
interesting phenomenon uncovered during these
studies was the drastic and detrimental effects on
27
the electrode performance due to chemical
impurities on the electrolyte surface.
www
.solar
One way this was proven was by measuring the
performance of the electrode placed on a single
-pv-management.com
crystal of YSZ with known impurities on the surface
(red dots), see figure 4. The electrode performance is also affected by the
grain size and grain boundary effects of the
The sample was then rinsed in hydrofluoric acid to deposited materials. These can vary from several
etch away the impure top surface and expose the tens of microns to as small as 100nm. This will
clean, pure YSZ layers underneath. After this, the form the subject of future studies with probes
sample was re-measured (blue squares) and the capable of improved spatial resolution. There will
Issue II 2009
electrode performance (measured as conductance also be influence from the thickness of the films
per unit of triple phase boundary length) was and their level of purity (1).
found to have improved by orders of magnitude,
with some transient behaviour during the first Benefits of hot stage microscopy
heating cycle (1). Using the Linkam system has enabled the
measurement of electrode properties a simple and
routine experiment. Accurate control of a lab-based
experiment is vital to be able to correlate with real-
life usage of the fuel cells. Setting up the REFERENCES
experiments is straightforward too with an optical Reference: Hertz, J.L.,
microscope being used to position the probes onto Rothschild, A., Tuller,
the surface of the electrodes. H.L., Highly enhanced
electrochemical
Efficient water-cooling enabled rapid turnaround performance of
between individual tests and hence it was easy to silicon-free
make multiple measurements to gain statistically platinum–yttria
viable data. stabilized zirconia
interfaces. J.
Lastly, by interfacing with LabView, it was possible Electroceramics,
to automate and run the experiments overnight 1385-3449 (Print)
Figure 2: The Linkam TS1500 hot stage system upping throughput. 1573-8663 (Online)
Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44