Secondary ion mass spectrometry was used to track an 18O tracer as it diffused into or out of Cu3Ba2YO7 through a BaF2 coating. It was found that, upon deposition, the Ba-rich nature of the coating initially bound up some of the O which diffused out of the Cu3Ba2YO7. Annealing at temperatures above 500C showed that O readily diffused through 100nm of BaF2. It was deduced that the diffusion coefficient for O in BaF2 was of the order of 10-11cm2/s.

Oxygen Tracer Diffusion through BaF2 and MgO Overcoats on YBa2Cu3O7-δ. S.B.Wong, J.J.Vajo, A.T.Hunter, C.W.Nieh: Applied Physics Letters, 1991, 59[6], 724-6

Table 155

Diffusion of Xe in BaF2 Specimens

(Irradiated to a total fast dose of 4 x 1016/cm2)