Dense yttria-stabilised zirconia electrolyte layers for SOFC by reactive magnetron sputtering

► Deposition of ∼1μm thin gas-tight 8YSZ electrolyte layers for SOFC by PVD. ► Influence of ion-assistance on the morphology of thin 8YSZ layers. ► Performance increase by 65% with regard to standard cells at 600°C. ► Up to 0.55Acm−2 at 600°C operating temperature. The morphology of layers of fully yttria-stabilised zirconia (YSZ) deposited by reactive magnetron sputtering was studied with regard to their application as thin electrolytes for solid oxide fuel cells (SOFC). A thin layer of YSZ was deposited on top of anode substrates for SOFC. The substrate comprises the warm-pressed anode itself, which supports the complete cell, and an anode functional layer deposited by vacuum slip casting, which is in direct contact with the electrolyte. From previous experiments it is known that non-assisted reactive DC magnetron sputtering produces layers with rather high leak-rate even when depositing at high temperatures. Residual pores on the substrates’ surfaces are responsible for the incomplete coverage by the thin electrolyte and are detrimental to the cell's performance. In the present paper, the effect of increasing bias power applied to the substrate is studied. A clear improvement of the layer morphology and gas-tightness can be observed with increasing bias power. SOFC single cell-tests show an improved performance with regard to standard wet-ceramic processing routes.