Preparation and superconducting behavior of triammonium fullerideстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 17 августа 2021 г.
Аннотация:The synthesis of triammonium fulleride (NH4)3C60 by ion exchange of either K3C60 or Rb3C60 with NH4Cl in absolute toluene is reported. According to the Rietveld refinement of a synchrotron radiation-based Xray diffraction pattern, (NH4)3C60 belongs to the same structure type as both K3C60 and Rb3C60 featuring an fcc lattice with intercalated cations occupying tetrahedral and octahedral cavities of the close-packing formed by fullerene С60 spheres. The ion exchange is incomplete and the final formulation of the product is [(NH4)2.88K0.12]C60. In contrast to earlier suggestions and tabulated ionic radii values, the (NH4)3C60 crystal structure is characterized by a lattice parameter slightly smaller than that of K3C60. A similarreaction between K4C60 and NH4Cl proceeds differently involving the redox step and affords [(NH4)0.48K2.52]C60 again emphasizing the fact that ammonium and potassium in the fulleride phase tend to form substitutional solid solutions. According to low-frequency inductive method, all (NH4)3C60-related phases studied are superconducting with similar temperatures of the superconducting transitionaround Tc=16.4 K.