Effect of Aluminum Fluoride on the Physical Properties and Stability of Fluorozirconate and Fluorozirco-Hafnate Glasses

The glass quality, physical properties, and thermal stability of fluorozirconate and fluorozirco-hafnate glasses were investigated as a function of the AIF3 content. The AlF3 concentration varied from 2 to 3.25 mol%. The ratio of the other components was constant, except for 50% substitution of ZrF4 by HfF4 in the fluorozirco-hafnate glasses. The physical properties of all the glasses were not affected strongly by the AlF3 content. However, the fluorozirco-hafnate glasses were prone to precipitate out AlF3 microcrystals for AlF3 contents greater than 3 mol%. The thermal stability of the glasses revealed a compositional dependence only in the case of the fluorozirco-hafnate glasses. The thermal stability decreased as the AlF3 content increased above 3 mol%. The authors concluded that the AlF3 microcrystals nucleated other fluoride phases such as zirconium-barium fluoride crystals.