Structure of the Mg2Ni switchable mirror: an EXAFS investigation

Abstract

Hydrogen intercalation changes both the structure and the optical properties of Mg 2 Ni thin films. The structure of evaporated thin films was investigated in the as-deposited, hydrogenated and dehydrogenated states with extended X-ray absorption fine structure (EXAFS) and X-ray diffraction (XRD). The partially crystalline virgin film becomes completely amorphous upon hydrogenation. After removal of the intercalated hydrogen the film remains amorphous. Hydrogen was detected in different concentrations in the virgin, hydrogenated and dehydrogenated films. Hydrogen loading was confirmed both by a shift of the nickel absorption edge and an increase of the hydrogen content. The intercalated hydrogen in the completely loaded film is located around the nickel atom with a coordination close to four.

The dielectric function of Mgy NiHx thin films ()

“…To test this hypothesis we calculate the dielectric functions of such a mixture in an effective medium theory and compare it with our measured results. In the Bruggeman approximation for spherical particles the effective dielectric function˜ of the mixture is implicitly given by [27]: sumed to be smaller than the wavelength of light which is fulfilled in these samples [24,28,29]. Fig.…”

Ab initiostudy of the effects of transition metal doping ofMg2NiH4

“…28 The high optical contrast opens up possibilities for Mg 2 Ni as a hydrogen sensing material. [29][30][31] For both applications the reaction enthalpy of the hydrogen desorption and absorption at typical operating conditions is too high. Preferable would be an equilibrium hydrogen pressure of 1 bar at room temperature.…”

Room-temperature hydrogen-induced resistivity response of Pd/Mg–Ni films

“…This material system is envisaged because the phase transitions come along with remarkable changes in electrical and optical properties, and therefore have the potential of being used in hydrogen sensing and optical switching processes. 5,[8][9][10][12][13][14][15][16] According to the data reported so far, some factors are found to have significant influence on the phase transitions of an Mg-Ni film. First, the relative contents of Mg and Ni are important.…”