Page 201 - High Temperature Solid Oxide Fuel Cells Fundamentals, Design and Applications

178 High Temperature Solid Oxide Fuel CeIIs: Fundamentals, Design and Applications

Oxygen Deficiency (moles)

Figure 7.4 Percent expansionasfunctionofoxygendeficiency in LaCrO, at 1000°CIZ 1-1 71.

7.2.3 Thermal Conductivity
The thermal conductivities of the SOFC components are all in the order of
1.5-2 W/(mK) [3]. These are low compared to 20 W/(mK) for stainless steel
and 400 W/(mK) for copper. Therefore, heat dissipation could be a problem
which must be considered in the SOFC design. This is particularIy true for higher
power density monolithic and planar SOFCs, but is less of a problem in the
tubular design.

7.2.4 Mechanical Strength
The mechanical strength of many compositions of LaCrOs is low compared to
YSZ (see Table 7.4) and appears to be variabIe. This low strength and variabiIity

Table 7.4 Mechanical strength of LaCr03 (MPa)
Dopant (mol%) Temperature ("C) Ref.

25 1000 (air) 1000 (Hz)
10% Mg 390-418 20
20% Mg 300 20
10% Sr 268 166 20
10% Sr 245 77 20
20% Sr 234 19
20% Sr 100 140 21
10% Ca 140 36 20
l5%Ca 80 40 13
20% Ca 100-150 20-60 50-60 13,22
30% Ca 100-140 60-130 20 13
YSZ 200 13