Elaboration, structures, and phase transitions for YFe{sub 2}D{sub x} compounds (x = 1.3, 1.75, 1.9, 2.6) studied by neutron diffraction
- CNRS, Thiais (France). Lab. de Chimie Metallurgique des Terres Rares
- Inst. Laue Langevin, Grenoble (France)
- CNRS, Gif sur Yvette (France). Lab. Leon-Brillouin
The structure of YFe{sub 2}D{sub x} deuterides (x = 1.3, 1.9, 1.75, and 2.6) have been studied by neutron diffraction (ND). The influence of a thermal treatment on the synthesis of YFe{sub 2}D{sub x} deuterides has been followed by in situ neutron diffraction for x = 1.3 and 1.9. After deuterium absorption at room temperature, their diffraction patterns show a mixture of YFe{sub 2} and a deuteride phase YFe{sub 2}D{sub y} (2.3 < y < 2.6). Heating the samples above 400 K for x = 1.3 and 425 K for x = 1.9, leads to a deuterium diffusion from the deuterium rich phase toward YFe{sub 2} to form a single phase deuteride with lower D content. Single phase deuterides YFe{sub 2}D{sub 1.3}, YFe{sub 2}D{sub 1.75}, and YFe{sub 2}D{sub 1.9} display superstructure lines which imply a lowering of symmetry compared to the cubic C15 structure of the parent intermetallic. YFe{sub 2}D{sub 1.3} crystallizes in the tetragonal I{bar 4} space group (Z = 20) with a = 11.985(2) {angstrom} and c = 7.622(1) {angstrom}, YFe{sub 2}D{sub 1.75} in the cubic I{bar 4}3m space group (Z = 64) with a = 15.336(2) {angstrom}, and YFe{sub 2}D{sub 1.9} in a tetragonal structure with a = 12.145(2) {angstrom} and c = 23.064(2) {angstrom}. The analysis of their ND patterns at 300 K shows for x = 1.3 and 1.75 an ordering of the deuterium atoms in some preferential tetrahedral Y2Fe2 sites and a ferromagnetic structure with 1.5 and 1.9 {micro}B/Fe, respectively. For YFe{sub 2}D{sub 1.3} and YFe{sub 2}D{sub 1.9} the superstructure lines disappear above 460 and 444 K, respectively, and they return to a C15 structure. The origin of the structural deviation and of the order-disorder transition is discussed in relation with deuterium and magnetic ordering. YFe{sub 2}D{sub 2.6} deuteride crystallizes at 300 K in the cubic Fd3m space group (Z = 8) with a = 7.785(2), deuterium atoms located statistically in tetrahedral Y2Fe2 sites and a ferromagnetic structure with a magnetic moment of 1.8 {micro}B/Fe.
- OSTI ID:
- 329128
- Journal Information:
- Journal of Solid State Chemistry, Vol. 142, Issue 1; Other Information: PBD: Jan 1999
- Country of Publication:
- United States
- Language:
- English
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