Chemical stability of ZrF4- and AlF3-based heavy metal fluoride glasses in water

Glasses of the compositions 50ZrF4–33BaF2–10YF3–7AlF3 and 40AlF3–12BaF2–22CaF2–16YF3–10SrF2 (mol%), respectively, were corroded in H2O for different times at 20–80°C. The cationic species Zr, Al, Ba, Y, etc. were measured by secondary neutral mass spectrometry, whereas H was measured by nuclear reaction analysis. In the case of the ZrF4-based glass the reaction depths follow at 20°C a dependence proportional to t, the attack time. This dependence changed with temperature as the t at 80°C. The H reaction profiles fit well into this scheme. In the case of the AlF3-based glass also a t-dependence is obtained at 80°C. Whereas the reaction layer peels off for the ZrF4-based glass for longer times (>1 h), it is relatively stable on the AlF3-based glass and protects it against further attack. The AlF3-based glass is about 10 times more stable in water than the ZrF4-based glass.