Phase change of sputtered LaNi5 thin films due to hydrogenation

Polycrystalline LaNi5 thin films were prepared by a co-sputtering method. Structural changes of the films after the hydrogen absorption-desorption cycles at different temperatures and after the heat treatment in a hydrogen atmosphere were investigated by X-ray diffraction (XRD) analysis. At room temperature, the sputtered films have much longer cyclic stability; however, the increase of temperature during hydriding-dehydriding process, and the hydrogen heat treatment at elevated temperatures speed up the disproportionation reaction or the segregation of the LaNi5 alloy thin film. A comparison of the results of the sputtered LaNi5 thin him with the previously reported data of the evaporated LaNi5 thin film shows a significant improvement of the him stability. (C) 1999 Elsevier Science S.A. All rights reserved.