Kinetics of the EVD process for growing thin zirconia/yttria films on porous alumina substrates

摘要

The electrochemical vapour deposition (CVD/EVD) method has proven to be a good technique to form thin, gas tight dense solid electrolyte or mixed conducting films on porous substrates. Applications of the so formed systems are in solid oxide fuel cells (SOFC), oxygen sensors, oxygen separation membranes and electrocatalytic reactors. In this paper, experimental results on the kinetics of the deposition by the EVD method of dense zirconia-yttria layers on porous [MATH]-alumina substrates are presented, and compared with theoretical models. The experimental work concerns mainly the effect of temperature on the growth rate of the EVD film. At 1000°C, layer growth occurs linear with time under current process conditions ; in this case diffusion of the oxygen source reactant in the substrate pores is the rate limiting step for the EVD process. Between 900°C and 1000°C the growth rate limitation changes to the electrochemical transport through the film, which is parabolic with time. This behaviour is predicted by the theoretical model.