PHASE STABILITY AND SOME PHYSICAL PROPERTIES OF THE YbCu₅-RELATED INTERMETALLICS

K. Yoshimura¹, N. Tsujii¹, J. He¹, T.Kawabata¹ , H. Michor², K. Kreiner², G. Hilscher², T. Miyano³, M. Kato¹ and K. Kosuge¹

¹Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
²Institute für Experimentalphysik, Technishe Universität Wien, Wiedner Hauptstrasse 8-10/131, A-1040 Wien, Austria
³Inorganic Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden

In the rare earth RE-Cu systems, the RECu₅ intermetallics crystallize in CaCu₅-type hexagonal structure or AuBe₅-type cubic structure. In this paper, we concentrate on the YbCu₅-related intermetallics. We have been studying the YbCu_5-xM_x systems with hexagonal (M=Al, Ga) and cubic (Ag, Au, Pd, In, Tl, Cd) structures from a view point of solid state physics and chemistry[1]. For the latter systems, mixed phases appears in the composition range 0²x²0.1, i.e. [Yb₂Cu₉ [2](C'phase) + Yb₂Cu₁₃ [3](H'phase)]. An alloy with the nominal composition YbCu₅ was prepared by Ar arc melting and then annealed at 750C. X-ray powder diffraction pattern of this sample showed that the sample consisits of C' and H' phases, i.e.two phase mixtures: YbCu₅ phase does not exist under ambient pressure against the paper of A.Iandelli & A. Palenzona [4], which clearly indicates the existence of YbCu₅ phase.

Recently, our group succeeded in preparing cubic YbCu₅ phase under the pressure of 1.5GPa at 900C[1]. The width of X-ray powder diffraction peaks of this cubic phase is very broad, more than two times of that of usual samples. We are now investigating the structure of ìcubic YbCu₅î from a microscopic point of view by use of TEM, SEM and EDX etc.. By the discovery of existence of cubic YbCu₅, the physical properties of substitutional systems YbCu_5-xM_x have been promoted better understanding through the whole composition range 0²x²1.

We expect to present the nature of "cubic YbCu₅" and the physical properties of YbCu₅-related compound.

1. K. Yoshimura, N. Tsujii, J. He, M. Kato, K. Kosuge, H. Michor, K. Kreiner, G. Hilscher, T. Goto: J. Alloy Comp., 262-263(1997)118-123
2. R. Cerny, M. François, K. Yvon, D. Jaccard, E. Walker, V. Petricek, I. Cisarova, H-U. Nissen, R. Wessicken: J. Phys. Condens. Matter 8(1996) 4485- 4493
3. J. Hornstra, K. H. J. Buschow: J. Less-Common Met., 27(1972)123-127
4. A. Iandelli, A. Palenzona: J. Less-Common Met., 25(1971) 333-335