Laves Phases Ln1–xEuxMg2 (Ln = La, Sm) and the Hydride La0.9Eu0.1Mg2Hy≤7
作者： Christian Reichert , Holger Kohlmann
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摘要: Mixed crystal Laves phases Ln1–xEuxMg2 (Ln = La, Sm) were prepared from the elements by melting reactions and characterized X-ray powder diffraction. In substitutional range 0 ≤ x 0.5 cubic of MgCu2 type, for 0.8 1 La) 0.9 Sm), respectively, hexagonal MgZn2 type are formed, separated each other a miscibility gap. The dependence lattice parameters on degree substitution follows closely Vegard behavior with a(La1–xEuxMg2 (0 0.5)) (8.798(3) + 0.00177(8)x) A a(Sm1–xEuxMg2 (8.629(2) 0.00404(7)x) A. Analysis unit cell volumes suggests europium to be divalent in all mixed phases. Hydrogenation as followed situ thermal analysis is exothermic compositions. For rich reaction products upon hydrogenation at 6 MPa hydrogen pressure an autoclave binary lanthanum hydride EuMg2H6, latter being unsubstituted according refined Rietveld analysis. lanthanum-rich compounds 0.1) ternary hydrides tetragonal LaMg2D7 structure if high enough (11 MPa), heating rates temperatures kept low (373 K). new La0.9Eu0.1Mg2Hy≤7 was diffraction data (space group P41212, 6.2592(1) A, c 9.3759(3) A, V 367.322(2) A3, Z 4).
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