The interdiffusion coefficients of Al-replacing elements were estimated by using diffusion couples of Al-rich pseudo-binary systems at 1423, 1473 and 1523K. The experimental data were analyzed by using the Sauer and Freise method, and the impurity diffusion coefficient of Nb was estimated by applying the Darken-Manning equation. The impurity diffusion coefficients could be described by the expression:

2.1 x 10-1exp[-479(kJ/mol)/RT]

The activation enthalpy confirmed retardation of Nb diffusion by the anti-site diffusion mechanism.

H.Fukaya, M.Moniruzzaman, Y.Murata, M.Morinaga, T.Koyama, W.Hashimoto, K.Tanaka, H.Inui: Defect and Diffusion Forum, 2010, 297-301, 384-9