Diffusivities of Hydrogen and Deuterium in Amorphous and Crystallized Pd–Si Based Alloys

Abstract

The diffusion coefficients of hydrogen and deuterium in amorphous and crystallized alloys (Pd₈₀Si₂₀, Pd₇₀Ni₁₀Si₂₀ and Pd₅₀Ni₃₀Si₂₀) were determined in the temperature range of 300 K to 600 K by the evolution method. Results obtained are as follows:
(1) The diffusion coefficients of hydrogen and deuterium in crystallized Pd₈₀Si₂₀ and Pd₇₀Ni₁₀Si₂₀, alloys were about 1.5–2.0 times as large as those in amorphous Pd₈₀Si₂₀ and Pd₇₀Ni₁₀Si₂₀ alloys. On the other hand, the diffusion coefficents of hydrogen and deuterium in a crystallized Pd₅₀Ni₃₀Si₂₀ alloy were almost equal to those in an amorphous Pd₅₀Ni₃₀Si₂₀ alloy.
(2) Generally, the activation energies for hydrogen and deuterium increased with increasing nickel content.
(3) The differences between the activation energies for hydrogen and those for deuterium in amorphous and crystallized alloys decreased with increasing nickel content.
A trial was made to interpret the above results semi-quantitatively by using the semi-quantum mechanical rate theory on diffusion introduced by Ebisuzaki et al.