Glass and glass-ceramics have been considered as the most
suitable sealing materials. They are easy to fabricate and possible to
prepare in a broad composition range. Glass and glass-ceramics,
when applied to sealing materials in SOFC, should fulfill a number
of conditions, including thermal, mechanical, chemical and struc-
tural properties [8,10–12]. The potential requirements are: the glass
transition temperature Tg should be below the operating tempera-
ture while relieving thermal stresses and self-healing cracks [13],
the thermal expansion coefficient should be similar to the values of
other fuel cell components between 8.0 and 13.0106
1C1[14–16], the resistivity should be high enough to protect electrica
loss (4104
Ω cm), sealing should be tightly bonded not to allow
any transportation of fuel gas and air to undesired components [7]
When a sealant fulfills those conditions, it is commonly applicable
to different parts between electrodes/electrolyte (ceramics) and
interconnect/frame (metals). There often occurs devitrification in
the glass and glass-ceramics when SOFC operates at high
temperature for a long time due to the crystallization of glass
The inhomogeneous structural state by a devitrification gives rise to
the reduction of the SOFC life-span, and thus a structural stability
has to be considered for the development of the sealing glass and
glass-ceramics [13].