Partial Stabilization of Tetragonal Zirconia in Oxynitride Glass-Ceramics

Nitrogen (via a polymeric AlN precursor) and ZrO2 are introduced into a MgO‐CaO‐Al2O3‐SiO2‐glass. Subsequent crystallization of the glass results in a fine‐grained oxynitride glass‐ceramic. The microstructure of the latter is found to be entirely different for nitrogen concentrations of 4.85 and 9.94 mol%. Not only do the phase contents differ, but also tetragonal zirconia is more effectively stabilized at higher nitrogen concentrations. Partial stabilization of tetragonal zirconia is not due to nitrogen incorporation but is based on an indirect effect: the spherical morphology of tetragonal zirconia precipitated at higher nitrogen contents suppresses the nucleation of the martensitic transformation. The beneficial effects of the introduction of nitrogen and the simultaneous incorporation of zirconia into a glass‐ceramic result in overall improved mechanical properties.