Electrochemical vapor deposition (EVD) of oxygen ion conducting and mixed conducting, oxygen-ionic/electronic, oxide layers is achieved at near atmospheric pressure process conditions by employing metals and metal compounds for removal and/or recovery of the free halogen byproduct of the EVD reaction. The metals and metal compounds are employed as solids, vapors, and as oxides in intimate mixture with carbon directly within the deposition zone together with the substrates to be coated. The process leads to significant cost reduction, for instance, in the fabrication of thin layers of solid oxygen ion conducting electrolytes, for fuel cells, gas separators, and gas sensors, when compared to state-of-the-art EVD processes which are conducted under vacuum conditions.