Effect of nanoparticle nature on hydrogen concentration profiles and improved switching characteristics in Gd switchable mirrors

A detailed elastic recoil detection analysis using 40 MeV ²⁸Si ⁵⁺ ions has been carried out to study the changes in the H concentration and concentration profiles during the hydrogenation/ dehydrogenation process in polycrystalline and nanoparticle Gd layers formed using vacuum evaporation and inert gas evaporation techniques, respectively. Nanoparticle sample exhibits a larger difference in the [H]/[Gd] values (2.9 and 1.7) in comparison to polycrystalline sample (2.4 and 2.0) in the loaded and deloaded states. Hydrogenation/dehydrogenation activity is restricted to the top portion in case of polycrystalline sample. In contrast to this, size induced structural transformation; enhanced surface area and the presence of large number of inter particle boundaries due to nanoparticle character result in the complete Gd layer becoming active during switching.