Mechanical Characterization of Solid Oxide Fuel Cells and Sealants

5
-
41
 
(a)
). 
The fracture shear stress of 15 MPa obtained in this test agreed with the one obtained in a 
subsequent test of another specimen at 800°C (16.5 MPa), which contrary to the previous test 
was rather unbiased by deformation of the steel (
Figure 
5
-
41
 
(a)
). The test at 760°C was not 
repeated again, since the further test was carried out at 800°C successfully, which is a more 

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Results and discussion 
124 
relative operation temperature in SOFC. The first specimen loaded initially at 660°C could 
sustain a higher torsion moment since it was tested below seal softening temperature. At this 
temperature the steel was less creep resistant than the sealant. The second specimen was tested 
above the softening temperature and hence a lower moment was necessary.
Hence, it can be concluded from these tests that pre-deformation due to plasticity of the 
Crofer22APU steel does not affect the maximum applied and sustained shear stress of the sealant 
material. The loading curve indicated that the maximum sustainable moment, at which plastic 
deformation of the steel started at 660°C was ~ 15 % lower than the sealant failure moment at 
RT, implying that at this temperature (below 
T
g
) the sealant has almost the same shear strength 
as at RT. At 760°C and 800°C the sustainable moment and, hence, also the shear strength was 
reduced by a factor of almost three due to softening of the sealant, but it is still higher than 
bending stress at 800°C.
Contrary to H-Ag that revealed the same failure mode at RT and high temperature in the torsion 
tests, the failure mode of H-F changed from interfacial failure at RT to cracking through the 
glass-ceramic at high temperatures (see 
Figure