X-ray diffraction measurements of the lattice constant were used to determine the diffusion coefficients. At 25C, the diffusivities of D in α-TaD0.05 and of H in α-TaH0.05 were equal to 1.4 x 10-6 and 1.3 x 10-6 cm2/s, respectively.
H.Züchner, E.Wicke: Zeitschrift für Physikalische Chemie, 1969, 67[1-3], 154-8