Electrochemical Vapor Deposition of Yttria‐Stabilized Zirconia Films

Tubular solid oxide fuel cells employ yttria‐stabilized zirconia electrolyte film as an oxygen ion conductor at high temperatures. These yttria‐stabilized zirconia electrolyte films are deposited by an electrochemical vapor deposition (EVD) process. The electrochemical transport of oxygen ions during the EVD process is analyzed by measuring the film growth as a function of EVD reaction time; the film growth is found to be parabolic with time. Wagner's transport theory for parabolic growth and the defect model for yttria‐stabilized zirconia have been used to calculate the average electronic transport number and the partial electronic conductivity of the electrolyte film. The analysis of the data revealed that the electrolyte film growth is controlled by diffusion of electrons. It is also shown that the electrochemical transport that occurs during EVD of the electrolyte is similar to the phenomena of oxygen semipermeability wherein electrons migrate from the low‐oxygen partial pressure side to the high‐oxygen partial pressure side, and oxygen ions migrate in the reverse direction maintaining charge neutrality.