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Interruptions within the galvanostatic treatment are due to the I/U-characteristic and impedance measurements. By means of SEM and EDS the electrode/electrolyte cross section was investigated with respect to deposited Cr-oxide in the cathode. Cr-compounds could not be detected throughout the cathode. In fig. lb) a whole stack assemply including a protective and a contact layer is shown.

Conclusion

Using the high velocity torch nozzles designed by the DLR and a careful adaptation of plasma spray parameters succeeded in the production of dense perovskite-type chromite and manganite layers on bipolar plates. The deposition onto structured bipolar plates was a challenge which could be successfully solved by developing a deposition process using a spray robot and by changing the gas channel geometry.

To impede the evaporation of chromium compounds from the interconnector surface and thus the degradation of the electrical performance of the SOFC cathode a protective ceramic layer was developed and successfully tested.

Up to now the VPS technique is the only method of producing reliable protecting layers for the bipolar plate.

References

(1) Köck, W., Martinz. H.-P.. Greiner, H., Janousek, M.:"Development and Processing of Metallic Cr Based Materials for SOFC Parts".

(2) Quadakkers, J., Greiner, H„ Köck, W„ "Metals and Alloys for High Temperature SOFC Application", Proc. of 1st SOFC Forum, Luzern, Switzerland p.525 (1994)

(3) Mühlberger, E., Kremith. R.D.:"System and Method for Plasma Coating", US-Patent 4 328 257, May 4,1982

(4) Smith, M.F.:' 'An Investigation of the Effects of Droplet Impact Angle in Thermal Spray Deposition", Proc.7th National Thermal Spray Conf., Boston, USA, p 603 (1994)

(5) Fendler, E., Henne, R., Ruckdäschel, R., Schmidt, H., „Protecting layers for the bipolar plate of planar solid oxide fuel cells produced by VPS", Proc. of 2nd SOFC Forum, Oslo, Norway, p. 269 (1996)

(6) B. Brückner, H. Landes, B. Rathjen, Proceed, of the.3rd Intern. Symp. on Solid Oxide Fuel Cells edited by S.C. Singhal and H. Iwahara, Vol. 93-4, p 641-648, (1993).

(7) H. Schmidt, B. Brückner and K. Fischer, Proc. of the 4th Int. Symposium on Solid Oxide Fuel Cells edited by M. Dokiya, O. Yamamoto, H.-Tagawa and S.C. Singhal, Vol. 95-1, p 869(1995)

(8) Günther, C., Beie, H.-J., Greil, P., Richter, F., „Parameters influencing the Longterm-Stability of the SOFC", Proc. of 2nd SOFC Forum, Oslo, Norway, p. 491 (1996)

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