Highly reflecting Y/Mg–H_x multilayered switchable mirrors

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• 作者：Giebels ; I.A.M.E. ; Isidorsson ; J. ; Kooij ; E.S. ; Remhof ; A. ; Koeman ; N.J. ; Rector ; J.H. ; van Gogh ; A.T.M. ; et. al.
• 关键词：61.10.Eq ; 68.65.+g ; 78.40.-q ; 78.66.-w ; 82.60.Cx ; 82.80.Fk ; Hydrogen in metals ; YMg hydride ; Switchable mirrors ; Optical properties ; Pressure-composition isotherms
• 刊名：Journal of Alloys and Compounds
• 出版年：2002
• 期刊代码：45_09258388
• 类别：ms
• 出版时间：January 17, 2002
• 卷：330-332
• 期：Complete
• 页码：875-881
• 文件大小：354 K

摘要

Optical, structural and thermodynamic properties of Y/Mg&ndash;H_x multilayered switchable mirrors are investigated and compared with YMgH_x-alloys and pure YH_x. Multilayers clearly have superior reflectance in the low-hydrogen state over the whole range of photon energies, 0.72<plankvω<3.5 eV, investigated in this work. In the transparent high-hydrogen state the absorption edge of the multilayers with the same overall composition is shifted in energy on increasing the individual layer thicknesses. Thus, the absorption edge is non-trivially depending on the distribution of Mg in the film. Moreover, the optical contrast of multilayers is much higher than for pure YH_x and their optical switching does not suffer from hysteretic effects. Finally, Mg and YH₂ transform almost at the same time to MgH₂ and YH₃, respectively, with a heat of formation of &minus;30.9 kJ/mol H in absorption and &minus;36.6 kJ/mol H in desorption.