Hydrogen induced structure and property changes in Eu3Si4
Artikel i vetenskaplig tidskrift, 2019

Hydrides Eu3Si4H2-X were obtained by exposing the Zintl phase Eu3Si4 to a hydrogen atmosphere at a pressure of 30 bar and temperatures from 25 to 300 degrees C. Structural analysis using powder X-ray diffraction (PXRD) data suggested that hydrogenations in a temperature range 25-200 degrees C afford a uniform hydride phase with an orthorhombic structure (Immm, a approximate to 4.40 angstrom, b approximate to 3.97 angstrom, c approximate to 19.8 angstrom), whereas at 300 degrees C mixtures of two orthorhombic phases with c approximate to 19.86 and approximate to 19.58 angstrom were obtained. The assignment of a composition Eu3Si4H2+x is based on first principles DFT calculations, which indicated a distinct crystallographic site for H in the Eu3Si4 structure. In this position, H atoms are coordinated in a tetrahedral fashion by Eu atoms. The resulting hydride Eu3Si4H2 is stable by -0.46 eV/H atom with respect to Eu3Si4 and gaseous H-2. Deviations between the lattice parameters of the DFT optimized Eu3Si4H2 structure and the ones extracted from PXRD patterns pointed to the presence of additional H in interstitials also involving Si atoms. Subsequent DFT modeling of compositions Eu3Si4H3 and Eu3Si4H4 showed considerably better agreement to the experimental unit cell volumes. It was then concluded that the hydrides of Eu3Si4 have a composition Eu3Si4H2+x (x < 2) and are disordered with respect to H in Si2Eu3 interstitials. Eu3Si4 is a ferromagnet with a Tc at about 120 K. Ferromagnetism is effectively quenched in Eu3Si4H2+x. The effective magnetic moment for both materials is 7.5 pg which is typical for compounds containing Eu2+ 4f(7) ions.

Rare earth metal silicides

Zintl phase hydrides

Zintl phases

Magnetic properties

Författare

Gustav Ek

Uppsala universitet

Reji Nedumkandathil

Stockholms universitet

Robert Johansson

Uppsala universitet

Jorge Montero

Université Paris-Est

Claudia Zlotea

Université Paris-Est

Mikael Andersson

Chalmers, Kemi och kemiteknik, Energi och material, Oorganisk miljökemi 2

Per Nordblad

Uppsala universitet

Chiu Tang

Diamond Light Source

Martin Sahlberg

Uppsala universitet

Ulrich Haussermann

Stockholms universitet

Journal of Solid State Chemistry

0022-4596 (ISSN) 1095-726X (eISSN)

Vol. 277 37-45

Ämneskategorier

Oorganisk kemi

Materialkemi

Den kondenserade materiens fysik

DOI

10.1016/j.jssc.2019.05.033

Mer information

Senast uppdaterat

2019-09-20