Preparations and applications of Highly Concentrated Metal Hydrides

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We have formed highly concentrated metal hydrides form intermetallic compounds to modify their electrical and magnetic properties as follows:1. The films of Mg_2NiH_x, FeTiH_x, LaNi_5H_x and LaCo_5h_x can be prepared. The films which are made on glas substrates by means of flash evaporation are reacted with hydrogen at a high pressure. The hydride films are very stable against several cycles of hydriding and dehydriding reactions.2. The absorption spectrum of the Mg_2NiH_x film shows that the absorption edge is located near 1.6eV. This agrees with the calculated value for Structure I (1.36eV), rather than that for structure II (0.8eV). This measurement is the first finding about the band gap of a semiconductive metal hydride.3. The Hall coefficients of LaNi_5H_x and LaCo_5H_x films have been measured as a function of hydrogen pressure and temperature. These substances show the anomalous Hall effect. It is likely that Ni or Co particles are segragated during hydrogen absorption.4. The hydrogen absorbing alloys have been developed, which are based on YCo_3 and partially substituted substituted with Ni or Fe for Co. We can control the equilibrium hydrogen pressure by variying the Ni or Fe content.5. The magnetic properties of the hydrides of Y(Co/Ni/Fe)_3 compounds depend strongly upon hydrogen composition.