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Increased transition temperature in superconducting Na2CsC60 by intercalation of ammonia

Nature volume 362, pages 433435 (01 April 1993) | Download Citation

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Abstract

A WIDE variety of alkali-metal fullerides (AxC60) have been prepared, with stoichiometries varying between 1=x=11 (refs 1,2). Most of the compounds with x = 3 are superconductors with unusually high transition temperatures (Tc) which increase with the size of the face-centred cubic unit cell3. The increase in Tc on lattice expansion is attributed to a decrease in the conduction band width, and therefore one ultimately expects a saturation or downturn of Tc followed by a metal–insulator transition. We have sought to explore this regime by expanding the A3C60 structure through intercalation of neutral molecules capable of solvating the A+ ions. Here we report that the reaction of ammonia with Na2CsC60 (Tc = 10.5K; lattice constant α = 14.132 Å) produces the compound (NH3)4Na2CsC60, which has an expanded unit cell (a = 14.473 Å) and an increased Tc of 29.6 K. The structure contains the Na(NH3)+4 cation on the octahedral site.

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Author information

Affiliations

  1. AT& T Bell Laboratories, 600 Mountain Avenue, Murray Hill, New Jersey 07974, USA

    • O. Zhou
    • , R. M. Fleming
    • , D. W. Murphy
    • , M. J. Rosseinsky
    • , A. P. Ramirez
    • , R. B. van Dover
    •  & R. C. Haddon
  2. Current address: Inorganic Chemistry Laboratory, University of Oxford,South Parks Road, Oxford 0X1 3QR, UK

    • M. J. Rosseinsky

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https://doi.org/10.1038/362433a0

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