The aim of this research is to study in detail thebehaviour of glassy bioactive coatings (Bioglazes®) on zirconiasubstrates with different stabilising agents. In the case of tetragonal Ce-PSZ,some phenomena arose by applying a glaze coating. The stabilising CeO2undergoes to an -even partially reversible- autoredox process (CeO2-Ce2O3),caused by migration of oxygen during the glazing process, (ZrO2 isknown as a proton and oxygen radical conducer at high temperatures), with amacroscopic effect of a grey-green colouring of the Ce-PSZ substrate below thecoated surface ("affected volume"). The migration of oxygen can assumean extent for which at the glazing temperature, about 1300_C, it is possiblethe chemical equilibrium shifts towards formation of Ce2O3.Grey-green is the own colour of Ce2O3. By eliminating thesealing action of the glaze towards atmosphere, oxygen can diffuse back insideCe-PSZ lattice, recovering the chemical and thermodynamic equilibrium conditionswith CeO2 and Ce2O3 and inducing a decolouringeffect in the Ce-PSZ ceramic back to a light colour. The bioactive glassutilised to produce the coatings is a calcium-silicophosphatic one, coded AP40.
