Ceramics-Silikáty 47, (4) 121 - 131 (2003) |
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INFLUENCE OF ZIRCONIA CeO₂ LATTICE STABILIZING AGENT ON BIOGLAZE COATING
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Krajewski Adriano 1, Ravaglioli Antonio 1, Mazzocchi Mauro 1,
Labanti Martino 2,
La Torretta Teresa 2,
Bezzi Giovanni 2,
Minoccari Gianloris 2
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1 ISTEC-CNR , Institute of Science and Technology for Ceramics - Italian National Research Council,
Via Granarolo 64, 480 18 Faenza, Italy
2 ENEA, Department of Engineering of Materials and Processes - National Agency for Environment and Energy,
Via Ravengana 186, 480 18 Faenza, Italy
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Keywords: Bioactive glass, Bioglaze®, Bioactive coating, Stabilised zirconia
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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. |
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