Hydrogen permeability study of the thin Pd-Ag alloy membranes in the temperature range across the α-β phase transition

A series of Pd-Ag membranes with different atomic ratio (Ag = 0, 5, 10, 15, 20 and 23%) was fabricated by controlling the chemical components in the electroless plating bath followed by thermal annealing of the deposited metals. Gas permeation of the membranes was examined at the temperature ranges at 100-300 °C. The hydrogen flux for the membranes of low Ag content gave a marked change giving a peak in the range of 170-200 °C, which was attributed to the α-β crystal phase transition of the hydride. The peak in hydrogen flux became less significant and appears as shoulder along with the increase of silver content. This observation coincides with the decrease of lattice size difference between α and β phase by the increase of Ag content in the Pd-Ag alloy. Improved durability of the alloy membrane (Ag > 20%) was demonstrated by cyclic change of gas and temperature and was attributed to the suppression of lattice expansion by alloying with more than 20% of silver.