Coloration Mechanism of Fe Ions in β-Quartz s.s. Glass-Ceramics with TiO2 and ZrO2 as Nucleation Agents

Shingo Nakane,Kosuke Kawamoto

doi:10.3389/fmats.2017.00007

Abstract

Transparent Li2O-Al2O3-SiO2 low-expansion glass-ceramics have an undesirable brown color owing to Fe ions as a contaminant, whereas the mother glass normally has a clear appearance. Elucidation of the coloration mechanism during crystallization is important for industry to develop highly transparent materials. In this study, the mother glass contained SiO2, Al2O3, and Li2O as its principal constituents and TiO2 and ZrO2 as nucleation agents. The amount of contaminant Fe ions in the form of Fe2O3 was 0.03 wt%. It was confirmed that the coloration was appeared by the coexistence of Fe and Ti ions in the glass matrix based on the experimental results using Ti-containing and Ti-free glasses with a composition identical to that of the glass matrix. The coordination and oxidation state of the Fe ions were not changed by the coexistence of Ti ion according to the results of XANES measurement. The coloration is considered to be due to the formation of Fe-O-Ti by the concentration of Fe and Ti ions in the glass matrix phase during the crystallization process.

Highlights

Li2O–Al2O3–SiO2 low-expansion glass-ceramics having β-quartz s.s. or β-spodumene s.s. as main precipitated crystal were developed by Stookey more than 50 years ago, the research and development of the material is still active, on their nucleation phenomena and improving their characteristics to apply them to various emerging applications (Bhattacharyya et al, 2010; Sakamoto and Yamamoto, 2010)
The objective of the present investigation is to elucidate the mechanism of the strong brown coloration caused by Fe ions in transparent β-quartz s.s. glass-ceramics in Li2O–Al2O3–SiO2 system
We speculate that the concentrations and the coexistence of Fe and Ti ions in the glass matrix phase may give the strong brown coloration in the glass-ceramics

Summary

Introduction

Li2O–Al2O3–SiO2 low-expansion glass-ceramics having β-quartz s.s. or β-spodumene s.s. as main precipitated crystal were developed by Stookey more than 50 years ago, the research and development of the material is still active, on their nucleation phenomena and improving their characteristics to apply them to various emerging applications (Bhattacharyya et al, 2010; Sakamoto and Yamamoto, 2010). The objective of the present investigation is to elucidate the mechanism of the strong brown coloration caused by Fe ions in transparent β-quartz s.s. glass-ceramics in Li2O–Al2O3–SiO2 system.

Results

Conclusion