Kinetics and Morphology of Electrochemical Vapour Deposited Thin Zirconia/Yttria Layers on Porous Substrates

By means of electrochemical vapour deposition (E VD), it is possible to grow thin (0.5-j pm), dense airconia/yttria layers on porous ceramic substrates. Kinetics of the EVD process, morphology and oxygen permeation properties of the grown layers are investigated. Very thin (0,.5 t-an) layers are grown at relatively low temperatures (700 SOO’C). Water vapour as reactant enhances the surface reaction rate at the solid oxide/oxygen source reactant interface. A transition occurs from pore dtj?iision (above 1000°C) to bulk electrochemical dtj$usion (below 9OO’C) as ratelimiting step jar layer growth. The zirconia/yttria solid solution is mainly deposited in the cubic phase; the layers grow in a typical columnar way and are polycrystalline. Oxygen permeation measurements show that the oxygen permeation flux through the zirconia/yttria layers is influenced by the layer thickness, morphology, presence of water vapour and the oxygen pressure gradient over the layer.