An electron microprobe study was made of single crystals at temperatures of between 1200 and 1331C, for compositions ranging from 0 to 20mol%YF3. For a given temperature, the value of the interdiffusion coefficient increased approximately exponentially with increasing YF3 content. As the YF3 content increased, the temperature dependence of the interdiffusion coefficient decreased (table 188). Extrapolation of the interdiffusion coefficient to 0%YF3, combined with the likely defect formation mechanism at infinite dilution, permitted the estimation of the impurity diffusion coefficient for Y in essentially pure CaF2. This could be described by:

D (cm2/s) = 58.7 exp[-83.6(kcal/mol)/RT]

R.G.Visser, W.F.Schiavi, M.F.Berard: Journal of the American Ceramic Society, 1975, 58[9-10], 438-41

Table 188

Arrhenius Parameters for the CaF2-YF3 System at 1200 to 1331C