Electrochromism in mischmetal-based AB<inf>2</inf> alloy hydride thin film

Electrical resistivity studies on mischmetal-substituted, C15 type AB 2 alloy (Mm0.2Tb0.8Co2) hydrides with varied hydrogen interstitial concentrations have been carried out in the temperature range 80-300 K. Hydrogen concentration-dependent metal-semiconductor-like transition has been observed and explained based on the charge transfer between hydrogen and the 3d band and the reduction in 6S component of the electron density. Polycrystalline thin film of the alloy capped with palladium has been obtained by electron beam evaporation technique on clean glass substrates. Switching properties from reflecting to a transparent state by electrochemical polarization in an alkaline electrolyte of pH 13 at room temperature have been investigated. In addition, the cyclic durability of the films has been studied and compared with that of rare-earth-based switchable mirror films. Preferential interstitial site occupancy for the hydrogen atoms has been analyzed based on the curent voltage characteristics of alloy thin film. © 2007 American Chemical Society.