Phases, kinetics and structure of alkali-C60 compounds: preparation of Rb3- and (Rb3-xKx)-C60 superconductors

Károly Holczer, Gordon R. Chalmers, John B. Wiley, Shiou Mei Huang, Richard B. Kaner, François Diederich, Robert L. Whetten

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1 Scopus citations


System exploration of the compound-formation kinetics, phase composition and super-conductivity of Rb:C60 mixtures, as diagnosed by X-ray crystallography and shielding diamagnetism measurements, reveals a single superconducting phase: f.c.c. Rb3C60 compound (a = 14.43 A ̊, Tc = 29.6 K) analogous to f.c.c. K3C60 (a = 14.26 A ̊, Tc = 19.2 K). The formation kinetics are interpreted in terms of staging, i.e., segregation and growth of several phase-separated compounds. The other prominent phase is b.c.c. Rb6C60, analogous to the A6C60 compounds (A =Cs, K) reported earlier, but there is also a b.c.t. Rb4C60 compound and indications of another phase intermediate between C60 and Rb3C60. In samples prepared from mixtures in the 2.2:1 to 2.8 range, the shielding reaches a maximum of >50%, a high value for powder samples, and the X-ray pattern is free of interfering phases. Also reported are indications of two mixed-alkali phases prepared in high yield and tentatively associated with Rb2K1C60 and Rb1K2C60 (Tc values near 28 and 22.5 K, respectively). In contrast to the always sharp onset for Rb3C60, these compounds exhibit the rounded onsets characteristic of residual inhomogeneity.

Original languageEnglish (US)
Pages (from-to)307-316
Number of pages10
JournalSynthetic Metals
Issue number3
StatePublished - Aug 1993
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry


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