The diffusion of Ca was studied in c-axis and a-axis oriented films by using secondary ion mass spectroscopy. The films were grown by pulsed laser deposition, and Ca(NO3)2 solutions were deposited onto the film surface and annealed at 300 to 870C in air. The rate of Ca diffusion was found to be the same in c-axis and a-axis oriented films. The activation energy for Ca diffusion was found to be 67kJ/mol. Fast diffusion along the grain boundaries was observed at below 700C, with an activation energy of 46kJ/mol. At 300C, the grain boundary diffusion coefficient was about 1.7 x 10-14cm2/s. This was 100 times higher than the corresponding bulk diffusion coefficient.

Determination of Ca Diffusion in YBCO Films by Secondary Ion Mass Spectroscopy. A.V.Berenov, S.R.Foltyn, C.W.Schneider, P.A.Warburton, J.L.MacManus-Driscoll: Solid State Ionics, 2003, 164[3-4], 149-58

Table 58

Diffusion of O in Cr2O3 at 1100C as a Function of Pressure