Intermetallic diffusion between the Pd layer and the porous metal support can limit the hydrogen permeability, and ultimately give rise to serious problems in the long-term stability of Pd alloy hydrogen separation membranes. In this study, we developed a multi-layered Pd-Ag membrane having a uniform-microstructure and thermally stable alloy composition by DC magnetron sputtering and Ag up-filling heat treatment. This multi-layered Pd-Ag alloy membrane was introduced in order to prevent Ag segregation, to block the intermetallic diffusion from the porous stainless steel (PSS), and to improve the stability of the membrane. Experimental results showed that the homogeneous Pd-Ag alloy membranes acted as an extremely effective diffusion barrier and provided significant improvement on the thermal stability over a period of 2000 h. (C) 2015 Elsevier B.V. All rights reserved.