Co-Sintering of Dense Electrophoretically Deposited YSZ Films on Porous NiO-YSZ Substrates for SOFC Applications
- PDF / 1,115,701 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 38 Downloads / 229 Views
K3.1.1
Co-Sintering of Dense Electrophoretically Deposited YSZ Films on Porous NiO-YSZ Substrates for SOFC Applications Giuseppe Savo, Alberto Rainer, Alessandra D’Epifanio, Silvia Licoccia, Enrico Traversa Department of Chemical Science and Technology, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy. ABSTRACT An original process for the preparation of YSZ dense films with a thickness lower than 10 µm over NiO-YSZ substrates is presented. This process involves the preparation of a green membrane of NiO-YSZ and subsequent electrophoretic deposition (EPD) of commercial YSZ powder on this polymer-rich membrane. A single thermal treatment allowed removal of the organic compounds, sintering of the layers and full densification of the electrolyte. INTRODUCTION Fuel cells are energy-conversion devices that transform chemical energy in electric power via the electrochemical combustion of fuel. SOFCs offer various advantages, such as greater efficiency with a wide range of fuels, negligible production of pollutants and suitable durability [1,2]. Performant SOFCs should have electrodes with good electro-catalytic properties to ensure more efficient fuel combustion and oxygen reduction and must be chemically and mechanically stable for long term operation. The electrolyte has to be a good ionic conductor to minimize ohmic loss and has to ensure gas tightness. Moreover, its thermal expansion coefficient (TEC) should be similar to the TECs of the electrodes. Conventional SOFCs consist of a Ni-YSZ composite anode, a YSZ electrolyte and a perovskite (most commonly doped-LaMnO3) cathode and show an operating temperature around 1000°C. Such a high temperature is needed because of the ionic conductivity characteristics of YSZ. To ensure a good power density the ohmic resistance of the electrolyte must be until around 0.15 Ω cm-2. Operating at intermediate temperature allows to reduce cost and to increase reliability of SOFCs. In the case of YSZ, this resistance value can be reached at 700°C with a 15 µm highquality dense film deposited on a porous supporting anode or cathode [3]. Several approaches have been reported in the literature for the deposition of such films: electrochemical vapour deposition (EVD) [4], low pressure plasma spraying [5,6], RF sputtering [7], colloidal processes such as slurry-based dip or spray coating [8]. In this work electrophoretic deposition (EPD) was selected as a technique to obtain thin dense electrolyte films. EPD is a well known process that allows to obtain compact ceramic coatings with thicknesses ranging from few micrometers to several millimeters [9,10], which has been applied also in SOFC application for the preparation of YSZ films [11-15]. This paper reports a different approach from the early papers that combines EPD with a cosintering process. Co-sintering has recently been investigated as a promising technique for the reduction of the number of thermal cycles needed for the preparation of SOFCs [16,17]. However, usually substrates are pre-fired at an int
Data Loading...
