IngentaConnect The Systems Ce-Al-(Si, Ge): Phase Equilibria and Physical Propert...

Authors: Flandorfer H.¹; Kaczorowski D.²; Gröbner J.³; Rogl P.¹; Wouters R.⁴; Godart C.^{5, 6}; Kostikas A.⁷

Source: Journal of Solid State Chemistry, Volume 137, Number 2, May 1998 , pp. 191-205(15)

Abstract:

The phase relations in the Ce-poor region of the ternary systems Al–Ce–(Ge, Si) were re-established at 600°C for Ce-concentrations up to 33 at.% Ce. The exact phase triangulation and structure determination for both systems were determined by EPMA and X-ray powder diffraction techniques. The homogeneity regions at 600°C were redetermined for the two phases within the section Ce(Al_xSi_1-x)₂: CeAl_1.46Si_0.54 (AlB₂-type) and CeAl_0.45–1.28Si_1.55–0.72 (ThSi₂-type). Besides these two phases, the only compound stable at 600°C in the system Al–Ce–Si was found to be CeAlSi₂ with a new structure type. CeAl₂Si₂ with the La₂O₂S-type, reported in earlier investigations, was shown to be metastable. Similarly, the existence of the phases reported earlier, “CeAl_1.25–1.75Si_2.75–2.25,” “Ce₂Al_3.5Si_4.5,” and “Ce₂Al₃Si₂,” was not confirmed at 500°C or 600°C. Ce₃Al₄Si₆ (Ce₃Al₄Si₆-type) was obtained in pure form after long-term annealing of melt spun samples at 500°C. For the Al–Ce–Ge system, our investigations at 600°C confirmed the five ternary compounds known from the existing literature. Homogeneity regions and location of the ternary phases were redefined. XAS and magnetic susceptibility measurements revealed a tripositive cerium ground state, ²F_5/2, in all the compounds studied. CeAl_1.2Si_0.8, CeAlSi₂, Ce₃Al₄Si₆, and Ce₂Al_1.6Ge_5.4 are antiferromagnets with T_N of 4.2, 3.7, 3.5, and 4.7 K, respectively. In turn, CeAl₂Si₂, CeAlGe, and Ce₂Al₃Ge₄ order ferromagnetically below 8, 5.6, and 11 K, respectively. The electrical resistivity of all these phases is characteristic of cerium intermetallics with pronounced crystal field effects. Copyright 1998 Academic Press.

Language: English

Document Type: Research article

Affiliations: 1: Institut für Physikalische Chemie, Universität Wien, Währingerstraße 42, Wien, A-1090, Austria 2: W. Trzebiatowski Institute for Low Temperature and Structure Research, Polish Academy of Science, Wroclaw, PL-50950, Poland 3: Material Science International, Nobelstraße 15, Stuttgart, D-70507, Germany 4: Katholieke Universiteit Leuven, Department of Metallurgy and Materials Engineering, de Croylaan 2, Heverlee, B-3001, Belgium 5: CNRS, UPR 209, Pl. A. Briand, Meudon, 92195, France 6: CNRS, LURE, University of Paris Sud, Orsay, 91405, France 7: Institute of Materials Science, NCSR, Demokritos, Aghia Paraskevi, Athens, Gr-15310, Greece

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The Systems Ce–Al–(Si, Ge): Phase Equilibria and Physical Properties