Ir coating prepared on Nb substrate by double glow plasma

Compact and adhesion IF coating was obtained on the surface of the Nb Substrate by double glow plasma method which had a deposition chamber and two cathodes. Argon gas was used as the working gas. The bias voltage of IF target and Nb Substrate were 950 V and -300 V, respectively. The chamber Pressure was 35 Pa. Microstructure and morphology of the IF coating was examined by the X-ray diffraction and scanning electron microscopy, respectively. The IF coating had a poly-crystalline structure with preferential growth orientation of (220) crystal plane. The deposition velocity was similar to 5.7 mu m/h. The good adhesion resulted from the buffer layer between the Nb substrate and the IF coating. The Nb concentration distributed gradiently along the depth of the buffer layer. Because the target and the substrate were the cathode electrodes, the Nb and Ir were continuously deposited and Sputtered out on the Nb substrate surface. For the higher bias voltage of the target, Sputtered Nb atoms Were Suppressed by intense Ir atoms and formed a mixed boundary layer on the Nb Substrate surface. With the IF and Nb deposition, the Nb element in the as-deposited film gradually decreased and led the Nb atoms content decrease in the boundary layer. (C) 2008 Elsevier Ltd. All rights reserved.