ic9b02308_si_001.pdf (1.86 MB)
YHO, an Air-Stable Ionic Hydride
journal contribution
posted on 2019-10-18, 17:48 authored by Nicolas Zapp, Henry Auer, Holger KohlmannMetal hydride oxides
are an emerging field in solid-state research.
While some lanthanide hydride oxides (LnHO) were
known, YHO has only been found in thin films so far. Yttrium hydride
oxide, YHO, can be synthesized as bulk samples by a reaction of Y2O3 with hydrides (YH3, CaH2), by a reaction of YH3 with CaO, or by a metathesis of
YOF with LiH or NaH. X-ray and neutron powder diffraction reveal an
anti-LiMgN type structure for YHO (Pnma, a = 7.5367(3) Å, b = 3.7578(2) Å,
and c = 5.3249(3) Å) and YDO (Pnma, a = 7.5309(3) Å, b = 3.75349(13)
Å, and c = 5.3192(2) Å); in other words,
a distorted fluorite type with ordered hydride and oxide anions was
observed. Bond lengths (average 2.267 Å (Y–O), 2.352 Å
(Y–H), 2.363 Å (Y–D), >2.4 Å (H–H
and
D–D), >2.6 Å (H–O and D–O), and >2.8
Å
(O–O)) and quantum-mechanical calculations on density functional
theory level (band gap 2.8 eV) suggest yttrium hydride oxide to be
a semiconductor and to have considerable ionic bonding character.
Nonetheless, YHO exhibits a surprising stability in air. An in situ X-ray diffraction experiment shows that decomposition
of YHO to Y2O3 starts at only above 500 K and
is still not complete after 14 h of heating to a final temperature
of 1000 K. YHO hydrolyzes in water very slowly. The inertness of YHO
in air is very beneficial for its potential use as a functional material.