▪ Abstract Metal-hydrogen (M-H) systems are interesting from both a theoretical and a practical point of view. M-H systems are utilized for energy-storage systems, in sensor applications, and in catalysis. These systems are often exploited as models for studying basic material properties, especially when the size of these systems is small and nonbulk-like contributions become dominant. Surfaces, nanocrystals, vacancy- and dislocation-rich materials, thin films, multilayers, and clusters as systems of major interest are addressed in this review. We show that the hydrogen solubility of M-H systems is strongly affected by the morphology and microstructure of and the stress between regions of different hydrogen concentration. For small-sized systems, surface- or interface-related sites become important and change the overall solubility as well as the phase boundaries of M-H systems. In thin films deposited on stiff substrates, compressive stresses evolve during hydrogen loading because the films are effective...

HYDROGEN IN METALS: Microstructural Aspects

It is shown that thin layers of palladium coated magnesium lanthanide alloys reversibly go through an optical transition by variation of the hydrogen concentration, just as has recently been shown for pure lanthanides. With these layers optical switches can be constructed that exhibit three different optical states: a color-neutral transparent state at high hydrogen concentration, a nontransparent dark absorbing state at intermediate hydrogen pressures, and a highly reflective metallic state at low hydrogen pressures. The ratio in transmission between the transparent state and the reflecting state is more than 1000.

Optical switches based on magnesium lanthanide alloy hydrides

Mg–Ni alloy thin films were prepared by dc magnetron sputtering using Mg and Ni targets, and their optical switching property for hydrogen exposure has been investigated. Pd-capped MgNix (0.1<x<0.3) films show a good switchable mirror property. Optical transmittance of these Mg-rich Mg–Ni thin films in the hydride state is much improved compared with that of Mg2Ni thin film. We speculate that the variation of the ratio of Mg2NiH4 to MgH2 formed in the hydride state may cause this difference. Such a wide modulation range of optical switching is important for the application of this material to energy efficient smart windows.

Optical switching of Mg-rich Mg–Ni alloy thin films

The dielectric properties of alpha-MgH2 are investigated in the photon energy range between 1 and 6.5 eV. For this purpose, a sample configuration and experimental setup are developed that allow bo ...

/pdf/optical-properties-of-mgh2-measured-in-situ-by-ellipsometry-6rmkewg4dl.pdf

Optical properties of MgH2 measured in situ by ellipsometry and spectrophotometry

Yttrium and lanthanum hydride films with switchable optical properties

The optical appearance of yttrium thin film electrodes can be electrochemically switched from mirrorlike to highly transparent by making use of the hydride-forming properties of Y. A strong alkaline solution is a suitable electrolytic environment for obtaining stable electrochromic electrodes. The presence of a thin Pd layer covering the Y electrode is essential in providing a sufficiently high electrocatalytic activity for the electrochemical charge-transfer reaction. Hydrogen is irreversibly bound in Y-dihydride and reversibly bound in Y-trihydride. The optical changes are reversible and are induced within a narrow hydrogen concentration range, making this typical electrode material interesting for application in a new type of electrochromic devices.

/pdf/optical-switching-of-y-hydride-thin-film-electrodes-a-3drx4nf66p.pdf

M. Kremers

Papers

Optical Switching of Y‐Hydride Thin Film Electrodes A Remarkable Electrochromic Phenomenon

Optical switching of Y-hydride thin film electrodes: a remarkable electrochromic phenomenon.

Optical Switching of Y-Hydride Thin Film Electrodes. A Remarkable Electrochromic Phenomenon.