In:
Zeitschrift für Kristallographie - Crystalline Materials, Walter de Gruyter GmbH, Vol. 233, No. 6 ( 2018-6-27), p. 399-409
Abstract:
Hydrogenation products of the Zintl phases AeTt ( Ae = alkaline earth; Tt = tetrel) exhibit hydride anions on interstitial sites as well as hydrogen covalently bound to Tt which leads to a reversible hydrogenation at mild conditions. In situ thermal analysis, synchrotron and neutron powder diffraction under hydrogen (deuterium for neutrons) pressure was applied to Ba Tt ( Tt =Ge, Sn). Ba Tt H y (1 〈 y 〈 1.67, γ-phases) were formed at 5 MPa hydrogen pressure and elevated temperatures (400–450 K). Further heating (500–550 K) leads to a hydrogen release forming the new phases β-BaGeH 0.5 ( Pnma , a =1319.5(2) pm, b =421.46(2) pm, c =991.54(7) pm) and α-BaSnH 0.19 ( Cmcm , a =522.72(6) pm, b =1293.6(2) pm, c =463.97(6) pm). Upon cooling the hydrogen rich phases are reformed. Thermal decomposition of γ-BaGeH y under vacuum leads to β-BaGeH 0.5 and α-BaGeH 0.13 [ Cmcm , a =503.09(3) pm, b =1221.5(2) pm, c =427.38(4) pm]. At 500 K the reversible reaction α-BaGeH 0.23 (vacuum)⇄β-BaGeH 0.5 (0.2 MPa deuterium pressure) is fast and was observed with 10 s time resolution by in situ neutron diffraction. The phases α-Ba Tt H y show a pronounced phase width (at least 0.09 〈 y 〈 0.36). β-BaGeH 0.5 and the γ-phases appear to be line phases. The hydrogen poor (α- and β-) phases show a partial occupation of Ba 4 tetrahedra by hydride anions leading to a partial oxidation of polyanions and shortening of Tt – Tt bonds.
Type of Medium:
Online Resource
ISSN:
2196-7105
,
2194-4946
DOI:
10.1515/zkri-2017-2142
Language:
English
Publisher:
Walter de Gruyter GmbH
Publication Date:
2018
SSG:
13
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