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

Glasses of the compositions 50ZrF 4 -33BaF 2 -10YF 3 -7AlF 3 and 40AlF 3 -12BaF 2 -22CaF 2 -16YF 3 -10SrF 2 (mol%), respectively, were corroded in H 2 O 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 ZrF 4 -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 AlF 3 -based glass also a √t-dependence is obtained at 80°C. Whereas the reaction layer peels off for the ZrF 4 -based glass for longer times (>1 h), it is relatively stable on the AlF 3 -based glass and protects it against further attack. The AlF 3 -based glass is about 10 times more stable in water than the ZrF 4 -based glass.