AUTHOR=Nakane Shingo , Kawamoto Kosuke 

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

JOURNAL=Frontiers in Materials

VOLUME=4

YEAR=2017

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2017.00007

DOI=10.3389/fmats.2017.00007

ISSN=2296-8016

ABSTRACT=<p>Transparent β-quartz <italic>s.s</italic>. glass-ceramics in Li<sub>2</sub>O–Al<sub>2</sub>O<sub>3</sub>–SiO<sub>2</sub> system 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 SiO<sub>2</sub>, Al<sub>2</sub>O<sub>3</sub>, and Li<sub>2</sub>O as its principal constituents and TiO<sub>2</sub> and ZrO<sub>2</sub> as nucleation agents. The amount of contaminant Fe ions in the form of Fe<sub>2</sub>O<sub>3</sub> 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 X-ray absorption near-edge structure 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.</p>