Preparation and microstructure characterization of anodic spark deposited barium titanate conversion layers

Anodic spark deposition (ASD) is an advanced plasma-electrochemical coating process to prepare polycrystailine, ceramic-like conversion coatings on me tal surfaces, As an example, polycrystalline barium titanate (BaTiO3) phase s have been prepared by the anodic conversion of metal substrate and the me tal ions in the electrolyte. By a combination of various characterization t echniques, the configuration of the coating was elucidated, On the metal su bstrate a thin (similar to 50 nm) passivating amorphous film of titania (Ti O2) first forms, which subsequently changes to anatase and rutile structure s. With increasing anodic potentials, a plasma-chemical conversion reaction starts, leading to the heterogeneous formation of BaTiO3 layers of 2-10 mu m thickness. The results of this study lead to the formulation of a model describing a polycrystalline and inhomogeneous layer configuration.