Development of improved cathodes for solid oxide fuel cells Page: 4 of 36
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1, Introduction
Background Statements
The purpose of this project is to develop an improved cathode for high temperature
fuel cells than is currently being employed.
This project is based on the need for a more stable and reliable cathode than is
currently being employed in high temperature solid oxide fuel cells (SOFC). The inability of
the LaMnQ3 based cathodes to withstand exposure to fuel gas without degrading their
performance is one of the foremost problems confronting the successful commercialization of
SOFC's.
As part of our DOE-BES program we have been investigating a number of conducting
perovskite systems. Recent results indicate that some of the compositions In these systems
possess electrical conductivity and stability towards reduction superior to the currently used
SOFC cathode, La 8Sr.2MnO3. These results are very encouraging and suggest that we have
the ability to develop an improved cathode for SOFC's. In this program we are expanding
our DOE-BES studies with the intent of developing a composition which will out-perform
La 8Sr.2MnO3 as a SOFC cathode.
In our DOE-BES program we have shown that the system La1.CaxCr1.yCoyO3 (x =
0.1-0.3 and y = 0.1-1.0) can be sintered to densities > 95% TD in air at 14000C and below.
The electrical conductivity (d.c.) measurements were made as a function of temperature and
in the oxygen activity range from 1 to 10'19 atm. Details of the Apparatus and experimental
setup are explained elsewhere.0) At 100rC and 1 atm. the conductivity ranges from 17 S/cm
to 58 S/cm for La 9Ca1Cr 9Co 103 and LaCa.3Cr 8Co.203, respectively. Stability studies were
done by quenching powder samples from 1000*0 and 10-19 atm. and subjecting quenched
powders to X-ray diffraction. X-ray diffraction patterns of reduced samples for y = 0.1, 0.2
and 0.3 showed no second phase indicating that these compositions are structurally stable
throughout the entire temperature and oxygen activity range studied.
The observed results on sintering, electrical conductivity and stability towards
reduction demonstrate that LaCrO3 can be sintered in air at 14000C and below with varying
the composition without the deterioration of either the electrical conductivity nor high
temperature stability of the resulting dense ceramics.1
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Anderson, H.U. Development of improved cathodes for solid oxide fuel cells, report, March 1, 1991; United States. (https://digital.library.unt.edu/ark:/67531/metadc1057574/m1/4/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.