Characterizing the residual glass in a MgO/Al2O3/SiO2/ZrO2/Y2O3 glass-ceramic

Abstract

The non-isochemical crystallization of glasses leads to glass-ceramics in which the chemical composition of the amorphous matrix differs from that of the parent glass. It is challenging to solely analyse the properties of these residual glassy phases because they frequently contain finely dispersed crystals. In this study, the composition of the residual glass matrix after the crystallization of a glass with the mol% composition 50.6 SiO2 · 20.7 MgO · 20.7 Al2O3 · 5.6 ZrO2 · 2.4 Y2O3 is analysed by scanning transmission electron microscopy (STEM) including energy dispersive X-ray analysis (EDXS). A batch of the residual glass with the determined composition is subsequently melted and selected properties are analysed. Furthermore, the crystallization behaviour of this residual glass is studied by X-ray diffraction, scanning electron microscopy including electron backscatter diffraction and STEM-EDXS analyses. The residual glass shows sole surface crystallization of indialite and multiple yttrium silicates while bulk nucleation does not occur. This is in contrast to the crystallization behaviour of the parent glass, in which a predominant bulk nucleation of spinel and ZrO2 is observed. The crystallization of the residual glass probably leads to different crystalline phases when it is in contact to air, rather than when it is enclosed within the microstructure of the parent glass-ceramics.

Surface Crystallization of a MgO/Y2O3/SiO2/Al2O3/ZrO2 Glass: Growth of an Oriented β-Y2Si2O7 Layer and Epitaxial ZrO2

“…Surprisingly, the glass-ceramics containing 2.4 mol% Y 2 O 3 also show high mechanical strengths although the low-QSS is not detected, which might be explained by the formation of spinel (CTE 20–800   °C  = 8 · 10 −6  K −1 )23 and ZrO 2 in its tetragonal or cubic form (CTE tetragonal  = 10.5 · 10 −6  K −1 )24 which also show large CTE values4. Furthermore, indialite was detected at the surface of these glass-ceramics and the crystallization of several different Y 2 Si 2 O 7 (YS) phases was obtained after longer crystallization at the second annealing step and various crystallization regimes25. In a previous experiment, the chemical composition of the residual glassy phase in the glass-ceramic was analyzed by scanning transmission electron microscopy (STEM) including energy-dispersive X-ray spectroscopy (EDXS) after crystallization at 950 °C for 5 h and 1060 °C for 1 h. Subsequently, a glass with this composition was melted and investigated25.…”

“…Furthermore, indialite was detected at the surface of these glass-ceramics and the crystallization of several different Y 2 Si 2 O 7 (YS) phases was obtained after longer crystallization at the second annealing step and various crystallization regimes25. In a previous experiment, the chemical composition of the residual glassy phase in the glass-ceramic was analyzed by scanning transmission electron microscopy (STEM) including energy-dispersive X-ray spectroscopy (EDXS) after crystallization at 950 °C for 5 h and 1060 °C for 1 h. Subsequently, a glass with this composition was melted and investigated25. In contrast to the parent glass, this glass shows the surface crystallization of different YS-phases and indialite, while bulk nucleation does not occur25.…”

“…In a previous experiment, the chemical composition of the residual glassy phase in the glass-ceramic was analyzed by scanning transmission electron microscopy (STEM) including energy-dispersive X-ray spectroscopy (EDXS) after crystallization at 950 °C for 5 h and 1060 °C for 1 h. Subsequently, a glass with this composition was melted and investigated25. In contrast to the parent glass, this glass shows the surface crystallization of different YS-phases and indialite, while bulk nucleation does not occur25.…”

“…However, β-, δ- and ε-YS have been shown to simultaneously occur in some YAG-containing glass-ceramics26272829 while α-YS was additionally observed in glass-ceramics grown from an SiO 2 -MgO-Al 2 O 3 -ZrO 2 -Y 2 O 3 glass with a higher Al content25. These results also illustrated that an X-ray diffraction (XRD)-analysis of these phases is problematic if they occur simultaneously due to multiple peak super positions, a problem illustrated in detail in ref.…”

“…This article provides a study on the crystallization of a glass with the mol% composition 54.7 SiO 2 ·10.9 Al 2 O 3 ·15.0 MgO·3.4 ZrO 2 ·16.0 Y 2 O 3 , which is the composition of a residual glass phase in glass-ceramics produced from a glass of the mol% composition 50.6 SiO 2 ·20.7 MgO·20.7 Al 2 O 3 ·5.6 ZrO 2 ·2.4 Y 2 O 3 425. This glass does not nucleate in the bulk25, but shows sole surface crystallization of four different YS-phases.…”