Ceramics-Silikáty 47 (4) 121-131 (2003)

INFLUENCE OF ZIRCONIA CeO₂ LATTICE STABILIZING AGENT ON BIOGLAZE COATING

A. Krajewski, A. Ravaglioli, M. Mazzocchi, M. Labanti, T. La Torretta, G. Bezzi, G. Minoccari

The aim of this research is to study in detail the behaviour of glassy bioactive coatings (Bioglazes^®) on zirconia substrates with different stabilising agents. In the case of tetragonal Ce-PSZ, some phenomena arose by applying a glaze coating. The stabilising CeO₂ undergoes to an -even partially reversible- autoredox process (CeO₂-Ce₂O₃), caused by migration of oxygen during the glazing process, (ZrO₂ is known as a proton and oxygen radical conducer at high temperatures), with a macroscopic effect of a grey-green colouring of the Ce-PSZ substrate below the coated surface ("affected volume"). The migration of oxygen can assume an extent for which at the glazing temperature, about 1300°C, it is possible the chemical equilibrium shifts towards formation of Ce₂O₃. Grey-green is the own colour of Ce₂O₃. By eliminating the sealing action of the glaze towards atmosphere, oxygen can diffuse back inside Ce-PSZ lattice, recovering the chemical and thermodynamic equilibrium conditions with CeO₂ and Ce₂O₃ and inducing a decolouring effect in the Ce-PSZ ceramic back to a light colour. The bioactive glass utilised to produce the coatings is a calcium-silicophosphatic one, coded AP40.

Keywords: Bioactive glass, Bioglaze®, Bioactive coating, Stabilised zirconia.