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

Sabrina Seidel,Wolfgang Wisniewski,Antje Gawronski,Christian Rüssel,Christian Patzig,Thomas Höche,Yongfeng Hu

doi:10.1038/srep34965

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.

Highlights

IntroductionIt was argued that the mismatch of the large CTE of both ZrO2 and spinel compared to the CTE of the residual glassy phase is most probably sufficient to produce high-strength glass-ceramics[7]
Produced glass-ceramics, containing tetragonal ZrO2 (CTE = 10.5 · 10−6 K−1 24) and spinel (MgAl2O4, CTE(20–800 °C) = 8 · 10−6 K−1 22), show excellent mechanical properties despite the absence of any QSS7
The composition of the residual glassy phase was determined using scanning transmission electron microscopy (STEM) in combination with energy-dispersive X-Ray spectroscopy (EDXS), and it was found that a considerable amount of Zr is still present in the residual glass, showing that not all Zr contributed to the crystallization of ZrO2 in these glass-ceramics

Summary

Introduction

It was argued that the mismatch of the large CTE of both ZrO2 and spinel compared to the CTE of the residual glassy phase is most probably sufficient to produce high-strength glass-ceramics[7] This argumentation followed the assumption that the CTE of the residual glass is close to the CTE of the original glass. This assumption has not been supported by experimental results because the residual glass frequently occurs in small pockets in the μm- or even nm-range This has made it very challenging to experimentally determine its properties so far, unless the crystalline phases were removed, e.g. by chemical etching, which is usually not possible without changing the residual glass itself. A batch of glass with the chemical composition of the residual glass, analysed using STEM-EDXS in the crystallized parent glass, was melted and analysed by methods including X-ray diffraction (XRD), electron backscatter diffraction (EBSD), XANES and multiple TEM techniques

Methods

Results

Conclusion