“…For example, Ru-Al alloys have been applied for jet engine components, bond coats for thermal barrier coatings, corrosion-and oxidation-protective coatings, and electrodes [1,2], whereas Ta-Al alloys have been applied for sulfidation and oxidation-protective coatings [3][4][5], heater materials [12][13][14], and electromagnetic shielding [15]. A previous paper [16] evaluated the oxidation behavior of Ru-Al multilayer coatings in 1% O 2 -99% Ar at 400-800 • C. In our co-sputtering system [16][17][18][19][20][21], the plasma sources focused on a circular track but not the center of the substrate-holder; thus, a multilayer coating with cyclical gradient concentration formed, as the substrate-holder was rotated in a low speed of 1-7 rpm. Such multilayer coatings were constructed by alloy sublayers with continuous variation in compositions, but not monolithic sublayers of distinct elements.…”