Yttrium hydride | Wikipedia audio article
Channel: wikipedia tts
Date: 24/10/2018

This is an audio version of the Wikipedia Article:
Yttrium hydride

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SUMMARY
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Yttrium hydride is a compound of hydrogen and yttrium. It is considered to be a part of the class of rare-earth metal hydrides. It exists in several forms, the most common being a metallic compound with formula YH2. YH2 has a face centred cubic structure, and is a metallic compound.  Under great pressure, extra hydrogen can combine to yield an insulator with a hexagonal structure, with a formula close to YH3. Hexagonal YH3 has a band gap of 2.6 eV. Under pressure of 12 GPa YH3 transforms to an intermediate state, and when the pressure increases to 22 GPa another metallic face centred cubic phase is formed.In 1996, it was shown that the metal-insulator transition when going from YH2 to YH3 can be used to change the optical state of windows from non-transparent to transparent. This report spurred a wave of research on metal hydride-based chromogenic materials and smart windows; gasochromic windows reacting to hydrogen gas and electrochromic structures where the transparency can be regulated by applying an external voltage. When containing a substantial amount of oxygen, yttrium hydride is also found to exhibit photochromic properties.