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Synthesis of pyrochlore-type oxides with unusually high valence, Ru5+, Rh4+, and Ir5+, by a high-pressure technique
Ce séminaire de l'ICMMO présenté par Dr. Ayako YAMAMOTO, (RIKEN Advanced Science Institute, Japon) il aura lieu dans les locaux de l'ICMMO dans la salle O. Kahn.
It is well known that pyrochlore-type compounds exhibit attractive properties driven by geometrical frustration. Especially, itinerant ones are attractive, because some of them show superconductivity or metal-insulator transition. Here I will present my recent study in synthesis, structure and properties of A2Ru2O7 (A=Hg,Cd,Ca,Tl), Tl2Rh2O7, and A2Ir2O7 (A=Hg,Cd,Ca,Tl).
All the compounds are prepared at 4 GPa by a cubic-anvil-type equipment. High-pressure method has advantages in suppressing the vaporization of high- volatile elements, stabilize unusual valence, and keeping oxygen stoichiometry. Most of ruthenium and rhodium oxides show metal-insulator transition or kink, and iridium ones show anomalous metallic feature. I will also present thermal stability of these compounds. The results tell us that each compound stays in delicate balance between cations.