Lithium self-diffusion in some heavy metal fluoride glasses

Li self-diffusion has been studied below Tg in a series of ZrF4–BaF2–LaF3–LiF glasses with LiF contents of 10, 20, and 30 mol%, respectively. The DLi∗ values range between about 10−12 and 10−15 cm2/s and increase with increasing LiF content from 10 to 20% by two orders of magnitude. The stable isotopes 6Li (enriched) and 7Li and an SNMS depth profiling were used. For the precision of the diffusion data an anhydrous vacuum deposition of the 6Li tracer on the highly reactive glass surfaces was essential. In the glass with 30 mol% LiF no Li mobility could be determined yet with the present diffusion method. The Li diffusion is discussed and it is tried to understand why it displays a differing behaviour compared to that of the Na diffusion in respective NaF-containing glasses.