A novel concept for a thin-film cell was developed at DLR Stuttgart, which is applied to a porous metallic carrier substrate in a multistage, integrated vacuum plasma spraying process. This allows large-area cell units with 20-30 micrometer thick electrolyte layers to be deposited in a simple manner. The properties of the thin plasma-sprayed electrolyte layers with their lamellar structure differ greatly from the properties of the layers produced by sintering. This paper focuses on the investigation of the influence of the process parameters in plasma spraying on the gas tightness and on the ionic conductivity of the electrolyte layers. The measurement results of the sprayed coatings examined are correlated with the results of the electrochemical measurements of the cells. The investigations contribute to improving the electrochemical performance of Solid Oxide Fuel Cells stacks, which can be operated at reduced temperatures from 750 to 800 deg C. Paper includes a German-language abstract.