Influence of the Bias Substrate Power on the GDC Buffer Layer

Tuesday, 25 July 2017: 11:20
Grand Ballroom West (The Diplomat Beach Resort)
E. Breaz (FEMTO ST UMR CNRS6174), E. Aubry (FEMTO ST), A. Billard (FEMTO ST UMR CNRS6174), N. Coton (FIAXELL), P. Coquoz (Fiaxell Sarl), A. Pappas (FIAXELL SARL), S. Diethelm (Ecole Polytechnique Fédérale de Lausanne (EPFL)), R. Ihringer (Fiaxell Sàrl), and P. Briois (FEMTO ST Institute UMR CNRS 6174)
Nowadays, the researchers that are working on the SOFC technology, are agree that it is necessary to decrease the operating temperature at 700°C(650-750 °C) of IT-SOFC technology, which currently is around 850-900°C for electrolyte supported cell used by the three main operators –Bloom, Hexis and Sun Fire. At this temperature the reactivity and the component cost of the cell decrease. Nevertheless, some interactions between the conventional electrolyte material (YSZ) and the cathode material (lanthanum based) are still present and it is necessary to include a ceria buffer layer to avoid the possible formation of an insulating pyrochlore structure La2Zr2O7 layer at the electrolyte-cathode interface. In ceria family, the best material regarding the ionic conductivity is the samaria doped ceria. However, the gadolinia doped ceria is the most employed from the cost point of view and the availability of gadolinium in comparison with samarium. This buffer layer avoids the reactivity between electrolyte and cathode, and presents a good anionic conductivity. It must be dense, thin and adherent on electrolyte, in order to be suitable for the surface treatment process.

In this paper, we present some recent results obtained on the gadolinia doped ceria coatings deposited by magnetron sputtering from metallic targets in argon-oxygen reactive gas mixtures with different substrate bias voltage. After a description of the experimental device, a first part will be dedicated to their chemical, microstructural and structural characterization (SEM, XRD,…) in relation with the magnetron sputtering deposition parameters. In a second part, the ionic transport characteristics of the half cell (Ni-YSZ/YSZ/GDC) will be investigated via impedance spectroscopy measurements performed at various temperatures up to 800°C under Ar-H2 gas mixtures. Finally, a complete cell test ((Ni-YSZ/YSZ/GDC/LSC) was performed with the Fiaxell Open Flanges test bench.

This study is carried out within the framework of the European territorial cooperation program INTERREG V A France-Switzerland. It has benefited from financial support from the EU through the European Regional Development Fund (ERDF- € 139,176) and the Swiss Confederation's contribution of CHF 134,173