Improved contacting by the use of silver in solid oxide fuel cells up to an operating temperature of 800 degrees C

In the following, a contacting variant for solid oxide fuel cells will be p resented in which the conductivity of the interconnect is ensured by contac t elements made of fine silver. To this end, the interconnect has holes thr ough which the contact elements of fine silver (99.9 wt% Ag) are introduced and then pressed. This pressing process and the thermal expansion of the s ilver during heating leads to a gastight joint. The silver penetrations are additionally soldered to render them capable of withstanding temperature c ycling. Contact resistance measurements and corrosion studies at 800 degree sC in air or Ar/4 vol.% H-2/3 vol.% H2O demonstrate the functionality of th e contacting variant under the described conditions. The experimental resul ts indicate that contacting by means of silver contact elements ensures lon g-term stability up to operating temperatures of 800 degreesC. Current tran smission via the silver contact elements means that a large number of mater ials are conceivable as the interconnect material. In the following applica tion, an FeCrAl steel (1.4767, Aluchrom Y Hf-trade name Krupp Thyssen Niros ta) with 5.7 wt.% aluminium was used. At the operating temperature, a dense aluminium oxide layer forms on its surface which prevents the vaporization , for example of chromium oxide species, during fuel cell operation. (C) 20 01 Kluwer Academic Publishers.