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Title: Hydrogenation induced structure and property changes in GdGa

Abstract

Hydrides GdGaH{sub x} were obtained by exposing the Zintl phase GdGa with the CrB structure to a hydrogen atmosphere at pressures from 1.5 to 50 bar and temperatures from 50 to 500 °C. Structural analysis by powder X-ray diffraction suggests that conditions with hydrogen pressures in a range between 15 and 50 bar and temperatures below 500 °C afford a uniform hydride phase with the NdGaH{sub 1.66} structure (Cmcm, a=3.9867(7) Å, b=12.024(2) Å, c=4.1009(6) Å) which hosts H in two distinct positions, H1 and H2. H1 is coordinated in a tetrahedral fashion by Gd atoms, whereas H2 atoms are inserted between Ga atoms. The assignment of the NdGaH{sub 1.66} structure is corroborated by first principles DFT calculations. Modeling of phase and structure stability as a function of composition resulted in excellent agreement with experimental lattice parameters when x=1.66 and revealed the presence of five-atom moieties Ga-H2-Ga-H2-Ga in GdGaH{sub 1.66}. From in situ powder X-ray diffraction using synchrotron radiation it was established that hydrogenation at temperatures above 200 °C affords a hydride with x≈1.3, which is stable up to 500 °C, and that additional H absorption, yielding GdGaH{sub 1.66}, takes place at lower temperatures. Consequently, GdGaH{sub 1.66} desorbs H above T=200more » °C. Without the presence of hydrogen, hydrides GdGaH{sub x} decompose at temperatures above 300 °C into GdH{sub 2} and an unidentified Gd-Ga intermetallics. Thus the hydrogenation of GdGa is not reversible. From magnetic measurements the Curie-Weiss constant and effective magnetic moment of GdGaH{sub 1.66} were obtained. The former indicates antiferromagnetic interactions, the latter attains a value of ~8 μ{sub B} which is typical for compounds containing Gd{sup 3+}ions. - Graphical abstract: Ferromagnetic GdGa absorbs hydrogen in two steps to yield antiferromagnetic GdGaH{sub 1.66}. Display Omitted - Highlights: • Elucidation of hydrogen uptake behavior of the rare earth gallide GdGa by in situ diffraction. • H-incorporation in GdGa leads to the formation of chain-like polyanions Ga-H-Ga-H-Ga. • H-incorporation in GdGa changes magnetism from ferromagnetic to antiferromagnetic.« less

Authors:
;  [1];  [2];  [3];  [4]; ;  [5];  [2];  [3];  [1]
  1. Department of Materials and Environmental Chemistry, Stockholm University, SE-10691 Stockholm (Sweden)
  2. Department Physics and Astronomy, Uppsala University, Box 516, SE-75210 Uppsala (Sweden)
  3. Department of Chemistry - Ångström Laboratory, Uppsala University, Box 538, SE-75121 Uppsala (Sweden)
  4. MAX IV Laboratory, Lund University, Box 118, SE-22100 Lund (Sweden)
  5. Department of Engineering Sciences, Uppsala University, Box 534, SE-75121 Uppsala (Sweden)
Publication Date:
OSTI Identifier:
22584160
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 239; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION; ANTIFERROMAGNETISM; ATOMS; CHROMIUM BORIDES; GADOLINIUM IONS; HYDRIDES; HYDROGEN; HYDROGENATION; INTERACTIONS; INTERMETALLIC COMPOUNDS; LATTICE PARAMETERS; MAGNETIC MOMENTS; ORTHORHOMBIC LATTICES; POWDERS; RARE EARTHS; SIMULATION; SYNCHROTRON RADIATION; X RADIATION; X-RAY DIFFRACTION

Citation Formats

Nedumkandathil, Reji, Kranak, Verina F., Johansson, Robert, Ångström, Jonas, Balmes, Oliver, Andersson, Mikael S., Nordblad, Per, Scheicher, Ralph H., Sahlberg, Martin, and Häussermann, Ulrich. Hydrogenation induced structure and property changes in GdGa. United States: N. p., 2016. Web. doi:10.1016/J.JSSC.2016.04.028.
Nedumkandathil, Reji, Kranak, Verina F., Johansson, Robert, Ångström, Jonas, Balmes, Oliver, Andersson, Mikael S., Nordblad, Per, Scheicher, Ralph H., Sahlberg, Martin, & Häussermann, Ulrich. Hydrogenation induced structure and property changes in GdGa. United States. doi:10.1016/J.JSSC.2016.04.028.
Nedumkandathil, Reji, Kranak, Verina F., Johansson, Robert, Ångström, Jonas, Balmes, Oliver, Andersson, Mikael S., Nordblad, Per, Scheicher, Ralph H., Sahlberg, Martin, and Häussermann, Ulrich. Fri . "Hydrogenation induced structure and property changes in GdGa". United States. doi:10.1016/J.JSSC.2016.04.028.
@article{osti_22584160,
title = {Hydrogenation induced structure and property changes in GdGa},
author = {Nedumkandathil, Reji and Kranak, Verina F. and Johansson, Robert and Ångström, Jonas and Balmes, Oliver and Andersson, Mikael S. and Nordblad, Per and Scheicher, Ralph H. and Sahlberg, Martin and Häussermann, Ulrich},
abstractNote = {Hydrides GdGaH{sub x} were obtained by exposing the Zintl phase GdGa with the CrB structure to a hydrogen atmosphere at pressures from 1.5 to 50 bar and temperatures from 50 to 500 °C. Structural analysis by powder X-ray diffraction suggests that conditions with hydrogen pressures in a range between 15 and 50 bar and temperatures below 500 °C afford a uniform hydride phase with the NdGaH{sub 1.66} structure (Cmcm, a=3.9867(7) Å, b=12.024(2) Å, c=4.1009(6) Å) which hosts H in two distinct positions, H1 and H2. H1 is coordinated in a tetrahedral fashion by Gd atoms, whereas H2 atoms are inserted between Ga atoms. The assignment of the NdGaH{sub 1.66} structure is corroborated by first principles DFT calculations. Modeling of phase and structure stability as a function of composition resulted in excellent agreement with experimental lattice parameters when x=1.66 and revealed the presence of five-atom moieties Ga-H2-Ga-H2-Ga in GdGaH{sub 1.66}. From in situ powder X-ray diffraction using synchrotron radiation it was established that hydrogenation at temperatures above 200 °C affords a hydride with x≈1.3, which is stable up to 500 °C, and that additional H absorption, yielding GdGaH{sub 1.66}, takes place at lower temperatures. Consequently, GdGaH{sub 1.66} desorbs H above T=200 °C. Without the presence of hydrogen, hydrides GdGaH{sub x} decompose at temperatures above 300 °C into GdH{sub 2} and an unidentified Gd-Ga intermetallics. Thus the hydrogenation of GdGa is not reversible. From magnetic measurements the Curie-Weiss constant and effective magnetic moment of GdGaH{sub 1.66} were obtained. The former indicates antiferromagnetic interactions, the latter attains a value of ~8 μ{sub B} which is typical for compounds containing Gd{sup 3+}ions. - Graphical abstract: Ferromagnetic GdGa absorbs hydrogen in two steps to yield antiferromagnetic GdGaH{sub 1.66}. Display Omitted - Highlights: • Elucidation of hydrogen uptake behavior of the rare earth gallide GdGa by in situ diffraction. • H-incorporation in GdGa leads to the formation of chain-like polyanions Ga-H-Ga-H-Ga. • H-incorporation in GdGa changes magnetism from ferromagnetic to antiferromagnetic.},
doi = {10.1016/J.JSSC.2016.04.028},
journal = {Journal of Solid State Chemistry},
number = ,
volume = 239,
place = {United States},
year = {Fri Jul 15 00:00:00 EDT 2016},
month = {Fri Jul 15 00:00:00 EDT 2016}
}