Hydrogen permeability of Nb-based alloy membranes have been analyzed in view of the new description
of hydrogen permeation based on hydrogen chemical potential in order to investigate the alloying effects
on the mobility of hydrogen atom, B. There is a liner relationship between the normalized hydrogen flux,
JL, and the PCT factor, fPCT. The mobility of hydrogen atom is expressed in a format of the Arrhenius
equation. Then, the alloying effects on the activation energy, E, and the pre-exponential factor, B0, have
been investigated. It is found that logarithm of the pre-exponential factor, lnB0, is proportional to the
activation energy, E. In other words, when one factor decreases by alloying, the other factor also
decreases linearly. As a result, the addition of ruthenium, tungsten and molybdenum into niobium
enhances the hydrogen diffusivity at low temperature below the intersection temperature