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| ECHA InfoCard | 100.033.689 |
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Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Yttrium hydride is a compound ofhydrogen andyttrium. It is considered to be a part of the class ofrare-earthmetal hydrides. It exists in several forms, the most common being a metallic compound with formula YH2. YH2 has aface-centred cubic structure, and is ametallic compound. Under great pressure, extra hydrogen can combine to yield an insulator with a hexagonal structure, with a formula close to YH3.[1] Hexagonal YH3 has aband 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 metallicface-centred cubic phase is formed.[2]
In 1996, it was shown that themetal-insulator transition when going from YH2 to YH3 can be used to change the optical state of windows from non-transparent to transparent.[3] This report spurred a wave of research onmetal hydride-basedchromogenic materials andsmart windows;gasochromic windows reacting to hydrogen gas andelectrochromic structures where the transparency can be regulated by applying an external voltage.[4] When containing a substantial amount of oxygen, yttrium hydride is also found to exhibit reversiblephotochromic properties.[5] This switchable optical property enables their utilization in many technological applications, such as sensors, goggles, and medical devices in addition to the smart windows. According to a research results, the strength of the photochromic response is found to decrease with increasing oxygen concentration in the film accompanied by anoptical band gap widening.[6]
Yttrium hydride is being looked at as a high temperature superconductor.[7]
Yttrium hydride is being looked at as aneutron moderator[8] for use in new nuclear reactor designs.
