Importance of oxidation and reduction of barium titanate in material science

Both oxygen deficiency and excess are possible in pure and doped barium titanate and do influence in a passive or active manner its properties. Their crystal engineering by gas reduction and/or oxidation is reviewed by ''high-lighting'' the aspects of chemical and crystallographic properties, dc-field degradation, electrooptics, and thin layer technology and plasma treatments. As a conclusion future trends in barium titanate technology and applications are mentioned.