The crystallization of MgO–Al2O3–SiO2–ZrO2 glass-ceramics with and without the addition of Y2O3 – a combined STEM/XANES study

Abstract

Glasses with the mol% composition of 51.9SiO₂/21.2Al₂O₃/21.2MgO/5.7ZrO₂ without and with the addition of 2.5 mol% Y₂O₃ were melted and subsequently transformed into glass-ceramics via annealing. Both glass-ceramics show strong differences in the microstructure and in the phase composition after crystallization at 950 °C for 5 h and subsequently at 1060 °C for different annealing times. In the glass without Y₂O₃, the main crystal phase is a quartz solid solution accompanied by the precipitation of ZrO₂ and spinel. By contrast, glass-ceramics without the presence of a quartz solid solution were observed after the crystallization of the Y₂O₃-containing glass, using the same heat treatment. This is confirmed by analytical scanning transmission electron microscopy analysis and X-ray absorption near-edge structure spectroscopy data gathered at the Zr L₂-, Y L_2,3-, Si K- and Al L-edges. Furthermore, using X-ray absorption spectroscopy the coordination of the respective elements is analysed, and changes of the coordination during crystallization are monitored.