Place of Electrophoretic Deposition Among Thin-Film Methods Adapted to the Solid Oxide Fuel Cell Technology: a Short Review

Abstract

Thin film technologies have attracted ever-growing interest in different industrial areas. Concerning solid oxide fuel cells (SOFCs), especially devices operating in the intermediate temperature range, such technologies are applied particularly for the deposition of dense, gas-tight electrolyte films with a thickness of several μm to decrease ohmic resistance and enhance the cell performance. The main requirements for the technology selected are its low cost, simplicity of the equipment used, short deposition time and flexibility regarding the cell shape. First, we overview thin-film technologies adapted to the deposition of SOFC functional layers, discussing their strengths and weaknesses, with special attention given to electrophoretic deposition (EPD) as being the most simple and cost-effective colloidal method to fabricate different electrolyte films. Then we present the contribution of our scientific group in the development of the EPD method. The preparation of stable suspensions for the EDP is one of the key requirements for its successful implementation and reproducibility; this was considered in detail and the effect of self-stabilization in suspensions based on nanopowders (7–15 nm), obtained by the method of laser evaporation with consequent condensation, was discussed. Such suspensions, exhibiting high positive ζ-potential values (30–50 mV), were shown to be suitable for EPD without the addition of dispersants or iodine. The requirements for the electrode substrates were formulated and a model of particle aggregation near the porous substrate surface was proposed. Deposition parameters were established for different electrolyte films – commonly used yttria-stabilized zirconia, single and multiply doped CeO2 and proton-conducting doped BaCeO3 electrolytes. As was shown, the deposition on the highly conducting cathode substrates is simpler to implement than the EPD on non-conducting anode substrates and, in addition, it produces high quality films which render high OCV values and superior SOFC performance.